AD835AR [ADI]

250 MHz, Voltage Output 4-Quadrant Multiplier; 250兆赫,电压输出4象限乘法器
AD835AR
型号: AD835AR
厂家: ADI    ADI
描述:

250 MHz, Voltage Output 4-Quadrant Multiplier
250兆赫,电压输出4象限乘法器

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250 MHz, Voltage Output  
4-Quadrant Multiplier  
a
AD835  
FUNCTIO NAL BLO CK D IAGRAM  
FEATURES  
Sim ple: Basic Function is W = XY + Z  
Com plete: Minim al External Com ponents Required  
Very Fast: Settles to 0.1% of FS in 20 ns  
DC-Coupled Voltage Output Sim plifies Use  
High Differential Input Im pedance X, Y and Z Inputs  
Low Multiplier Noise: 50 nV/ Hz  
X = X1 –X2  
XY  
X1  
X2  
AD835  
XY + Z  
+1  
W OUTPUT  
Y1  
Y2  
APPLICATIONS  
Very Fast Multiplication, Division, Squaring  
Wideband Modulation and Dem odulation  
Phase Detection and Measurem ent  
Sinusoidal Frequency Doubling  
Video Gain Control and Keying  
Y = Y1 –Y2  
Z INPUT  
Voltage Controlled Am plifiers and Filters  
P RO D UCT D ESCRIP TIO N  
P RO D UCT H IGH LIGH TS  
T he AD835 is a complete four-quadrant voltage output analog  
multiplier fabricated on an advanced dielectrically isolated  
complementary bipolar process. It generates the linear product  
of its X and Y voltage inputs, with a –3 dB output bandwidth of  
250 MHz (a small signal rise time of 1 ns). Full-scale (–1 V to  
+1 V) rise/fall times are 2.5 ns (with the standard RL of 150 )  
and the settling time to 0.1% under the same conditions is typi-  
cally 20 ns.  
1. T he AD835 is the first monolithic 250 MHz four quadrant  
voltage output multiplier.  
2. Minimal external components are required to apply the  
AD835 to a variety of signal processing applications.  
3. High input impedances (100 kʈ2 pF) make signal source  
loading negligible.  
4. High output current capability allows low impedance loads  
to be driven.  
Its differential multiplication inputs (X, Y) and its summing in-  
put (Z) are at high impedance. T he low impedance output volt-  
age (W) can provide up to ±2.5 V and drive loads as low as  
25 . Normal operation is from ±5 V supplies.  
5. State of the art noise levels achieved through careful device  
optimization and the use of a special low noise bandgap volt-  
age reference.  
T hough providing state-of-the-art speed, the AD835 is simple  
to use and versatile. For example, as well as permitting the addi-  
tion of a signal at the output, the Z input provides the means  
to operate the AD835 with voltage gains up to about ×10. In  
this capacity, the very low product noise of this multiplier  
(50 nVHz) makes it much more useful than earlier products.  
6. Designed to be easy to use and cost effective in applications  
which formerly required the use of hybrid or board level  
solutions.  
T he AD835 is available in an 8-pin plastic mini-DIP package  
(N) and an 8-pin SOIC (R) and is specified to operate over the  
–40°C to +85°C industrial temperature range.  
REV. A  
Inform ation furnished by Analog Devices is believed to be accurate and  
reliable. However, no responsibility is assum ed by Analog Devices for its  
use, nor for any infringem ents of patents or other rights of third parties  
which m ay result from its use. No license is granted by im plication or  
otherwise under any patent or patent rights of Analog Devices.  
© Analog Devices, Inc., 1994  
One Technology Way, P.O. Box 9106, Norw ood. MA 02062-9106, U.S.A.  
Tel: 617/ 329-4700  
Fax: 617/ 326-8703  
AD835–SPECIFICATIONS(T = +25؇C, V = ؎5 V, R = 150 , C 5 pF unless otherwise noted)  
A
S
L
L
Model  
AD 835AN/AR  
( X 1 – X 2)(Y1 – Y 2)  
W =  
+ Z  
T RANSFER FUNCT ION  
U
P ar am eter  
Conditions  
Min  
Typ  
Max  
Unit  
INPUT CHARACT ERIST ICS (X, Y)  
Differential Voltage Range  
VCM = 0  
±1  
V
Differential Clipping Level  
Low Frequency Nonlinearity  
؎1.2  
±1.4  
0.3  
0.1  
V
% FS  
% FS  
X = ±1 V, Y = 1 V  
Y = ±1 V, X = 1 V  
T MIN to T MAX  
0.5  
0.3  
1
vs. T emperature  
X = ±1 V, Y = 1 V  
Y = ±1 V, X = 1 V  
0.7  
0.5  
+3  
% FS  
% FS  
V
Common-Mode Voltage Range  
Offset Voltage  
vs. T emperature  
CMRR  
–2.5  
±3  
؎20  
±25  
mV  
mV  
dB  
1
T MIN to TMAX  
f 100 kHz; ±1 V p-p  
70  
Bias Current  
10  
20  
27  
µA  
µA  
µA  
kΩ  
pF  
dB  
dB  
1
vs. T emperature  
Offset Bias Current  
Differential Resistance  
Single-Sided Capacitance  
Feedthrough, X  
T MIN to T MAX  
2
100  
2
X = ±1 V, Y = 0 V  
Y = ±1 V, X = 0 V  
–46  
–60  
Feedthrough, Y  
DYNAMIC CHARACT ERIST ICS  
–3 dB Small-Signal Bandwidth  
–0.1 dB Gain Flatness Frequency  
Slew Rate  
Differential Gain Error, X  
Differential Phase Error, X  
Differential Gain Error, Y  
Differential Phase Error, Y  
Harmonic Distortion  
150  
250  
15  
MHz  
MHz  
V/µs  
W = –2.5 V to +2.5 V  
f = 3.58 MHz  
f = 3.58 MHz  
f = 3.58 MHz  
f = 3.58 MHz  
X or Y = 10 dBm, 2nd and 3rd Harmonic  
Fund = 10 MHz  
Fund = 50 MHz  
1000  
0.3  
0.2  
0.1  
0.1  
%
Degrees  
%
Degrees  
–70  
–40  
20  
dB  
dB  
ns  
Settling T ime, X or Y  
T o 0.1%, W = 2 V p-p  
SUMMING INPUT (Z)  
Gain  
–3 dB Small-Signal Bandwidth  
Differential Input Resistance  
Single Sided Capacitance  
Maximum Gain  
From Z to W, f 10 MHz  
0.990  
0.995  
250  
60  
2
50  
MHz  
kΩ  
pF  
X, Y to W, Z Shorted to W, f = 1 kHz  
dB  
Bias Current  
50  
µA  
OUT PUT CHARACT ERIST ICS  
Voltage Swing  
±2.2  
±2.0  
±2.5  
V
V
1
vs. T emperature  
T MIN to T MAX  
Voltage Noise Spectral Density  
Offset Voltage  
X = Y = 0, f < 10 MHz  
50  
±25  
nV/Hz  
mV  
mV  
؎75  
±10  
1
vs. T emperature2  
T MIN to T MAX  
Short Circuit Current  
Scale Factor Error  
75  
±5  
mA  
؎8  
±9  
؎1.0  
±1.25  
% FS  
% FS  
% FS  
% FS  
1
vs. T emperature  
T MIN to T MAX  
Linearity (Relative Error)3  
vs. T emperature  
±0.5  
1
T MIN to T MAX  
POWER SUPPLIES  
Supply Voltage  
For Specified Performance  
Quiescent Supply Current  
vs. T emperature  
PSRR at Output vs. Vp  
PSRR at Output vs. Vn  
±4.5  
±5  
16  
±5.5  
25  
26  
0.5  
0.5  
V
mA  
mA  
%/V  
%/V  
1
T MIN to T MAX  
+4.5 V to +5.5 V  
–4.5 V to –5.5 V  
NOT ES  
1T MIN = –40°C, T MAX = +85°C.  
2Normalized to zero at +25°C.  
3Linearity is defined as residual error after compensating for input offset, output voltage offset and scale factor errors.  
All min and max specifications are guaranteed. Specifications in boldface are tested on all production units at final electrical test.  
Specifications subject to change without notice.  
–2–  
REV. A  
AD835  
ABSO LUTE MAXIMUM RATINGS1  
P IN CO NNECTIO NS  
8-P in P lastic D IP (N)  
8-P in P lastic SO IC (R)  
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±6 V  
Internal Power Dissipation2 . . . . . . . . . . . . . . . . . . . . 300 mW  
Operating T emperature Range . . . . . . . . . . . . . –40°C to +85C  
Storage T emperature Range . . . . . . . . . . . . –65°C to +150°C  
Lead T emperature, Soldering 60 sec . . . . . . . . . . . . . . +300°C  
Y1  
Y2  
VN  
Z
1
2
3
4
8
7
6
5
X1  
X2  
VP  
W
AD835  
TOP VIEW  
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1500 V  
NOT ES  
(Not to Scale)  
1Stresses above those listed under “Absolute Maximum Ratings” may cause  
permanent damage to the device. T his is a stress rating only and functional  
operation of the device at these or any other conditions above those indicated in the  
operational sections of this specification is not implied. Exposure to absolute  
maximum ratings for extended periods may affect device reliability.  
2T hermal Characteristics:  
O RD ERING GUID E  
Tem perature Range  
8-Pin Plastic DIP (N): θJC = 35°C/W; θJA = 90°C/W  
8-Pin Plastic SOIC (R): θJC = 45°C/W; θJA = 115°C/W.  
Model  
P ackage O ptions*  
AD835AN  
AD835AR  
–40°C to +85°C  
–40°C to +85°C  
N-8  
R-8  
*N = Plastic DIP; R = Small Outline IC Plastic Package (SOIC).  
Typical Performance Characteristics  
DG DP (NTSC)  
FIELD = 1 LINE = 18  
Wfm FCC COMPOSITE  
0.00  
0.06  
0.11  
0.16  
0.19  
0.20  
0.4  
0.2  
X, Y, Z CH = 0dBm  
R
C
= 150Ω  
5pF  
L
L
0.0  
MIN = 0.00  
2
0
180  
90  
MAX = 0.20  
p-p/MAX = 0.20  
–0.2  
–0.4  
GAIN  
1ST  
0.00  
2ND  
0.02  
3RD  
0.02  
4TH  
0.03  
5TH  
0.03  
6TH  
0.06  
–2  
–4  
–6  
–8  
–10  
0
PHASE  
–90  
–180  
0.3  
0.2  
0.1  
0.0  
MIN = 0.00  
MAX = 0.06  
p-p = 0.06  
–0.1  
–0.2  
–0.3  
1M  
10M  
100M  
1G  
1ST  
2ND  
3RD  
4TH  
5TH  
6TH  
FREQUENCY – Hz  
Figure 3. Gain & Phase vs. Frequency of X, Y, Z Inputs  
Figure 1. Typical Com posite Output Differential Gain &  
Phase, NTSC for X Channel; f = 3.58 MHz, RL = 150 Ω  
DG DP (NTSC)  
FIELD = 1 LINE = 18  
Wfm  
0.00  
FCC COMPOSITE  
0.00  
0.01  
–0.00  
–0.01  
–0.20  
0.3  
0.2  
MIN = –0.02  
MAX = 0.01  
p-p/MAX = 0.03  
X, Y CH = OdBm  
R
C
= 150Ω  
5pF  
L
L
0.1  
0.0  
0
–0.1  
–0.2  
–0.3  
–0.4  
–0.5  
–0.6  
–0.1  
–0.2  
–0.3  
1ST  
0.00  
2ND  
0.03  
3RD  
0.04  
4TH  
0.07  
5TH  
0.10  
6TH  
0.16  
0.20  
0.10  
0.00  
MIN = 0.00  
MAX = 0.16  
p-p = 0.16  
–0.10  
–0.20  
300k  
1M  
10M  
FREQUENCY – Hz  
100M  
1G  
1ST  
2ND  
3RD  
4TH  
5TH  
6TH  
Figure 4. Gain Flatness to 0.1 dB  
Figure 2. Typical Com posite Output Differential Gain &  
Phase, NTSC for Y Channel; f = 3.58 MHz, RL = 150 Ω  
REV. A  
–3–  
AD835  
X, Y CH = 5dBm  
R
C
= 150  
< 5pF  
L
L
–10  
–20  
–30  
–40  
–50  
–60  
0
20  
40  
60  
80  
Y FEEDTHROUGH  
X FEEDTHROUGH  
X FEEDTHROUGH  
Y FEEDTHROUGH  
10M  
1M  
100M  
FREQUENCY – Hz  
1G  
1M  
10M  
100M  
1G  
FREQUENCY – Hz  
Figure 5. X and Y Feedthrough vs. Frequency  
Figure 8. CMRR vs. Frequency for X or Y Channel,  
RL = 150 , CL 5 pF  
0dBm ON SUPPLY  
X, Y = 1V  
–10  
–20  
–30  
–40  
–50  
–60  
PSRR ON V+  
0.200V  
GND  
PSRR ON V–  
–0.200V  
100mV  
10ns  
300k  
1M  
10M  
100M  
1G  
FREQUENCY – Hz  
Figure 9. PSRR vs. Frequency for V+ and VSupply  
Figure 6. Sm all Signal Pulse Response at W Output, RL =  
150 , CL 5 pF, X Channel = ±0.2 V, Y Channel = ±1.0 V  
10MHz  
1V  
GND  
–1V  
10dB/DIV  
30MHz  
20MHz  
500mV  
10ns  
Figure 10. Harm onic Distortion at 10 MHz; 10 dBm Input  
Figure 7. Large Signal Pulse Response at W Output, RL =  
to X or Y Channels, RL = 150 , CL = 5 pF  
150 , CL 5 pF, X Channel = ±1.0 V, Y Channel = ±1.0 V  
–4–  
REV. A  
AD835  
15  
10  
5
OUTPUT OFFSET DRIFT WILL  
TYPICALLY BE WITHIN SHADED AREA  
50MHz  
0
10dB/DIV  
150MHz  
100MHz  
–5  
–10  
–15  
OUTPUT V DRIFT, NORMALIZED TO 0 AT 25°C  
OS  
–55  
–35  
–15  
5
25  
45  
65  
85  
105  
125  
TEMPERATURE – °C  
Figure 11. Harm onic Distortion at 50 MHz, 10 dBm Input  
Figure 14. VOS Output Drift vs. Tem perature  
to X or Y Channel, RL = 150 , CL 5 pF  
35  
X CH = 6dBm  
Y CH = 10dBm  
30  
25  
20  
15  
10  
5
100MHz  
R
= 100  
L
200MHz  
300MHz  
10dB/DIV  
0
0
20  
40  
60  
80 100 120 140 160 180 200  
RF FREQUENCY INPUT X CHANNEL – MHz  
Figure 15. Fixed LO on Y Channel vs. RF Frequency  
Input to X Channel  
Figure 12. Harm onic Distortion at 100 MHz, 10 dBm Input  
to X or Y Channel, RL = 150 , CL 5 pF  
35  
X CH = 6dBm  
Y CH = 10dBm  
RL = 100  
30  
+2.5V  
GND  
25  
20  
15  
10  
5
–2.5V  
1V  
10ns  
0
0
20  
40  
60  
80 100 120 140 160 180 200  
LO FREQUENCY ON Y CH – MHz  
Figure 16. Fixed IF vs. LO Frequency on Y Channel  
Figure 13. Maxim um Output Voltage Swing, RL = 50 ,  
CL 5 pF  
REV. A  
–5–  
AD835  
P RO D UCT D ESCRIP TIO N  
Simplified representations of this sort, where all signals are pre-  
sumed to be expressed in volts, are used throughout this data  
sheet, to avoid the needless use of less-intuitive subscripted vari-  
ables (such as VX1). We can view all variables as being normal-  
ized to 1 V. For example, the input X can either be stated as  
being in the range –1 V to +1 V, or simply –1 to +1. T he latter  
representation will be found to facilitate the development of new  
functions using the AD835. T he explicit inclusion of the de-  
nominator, U, is also less helpful, as in the case of the AD835, if  
it is not an electrical input variable.  
T he AD835 is a four-quadrant, voltage output, analog multi-  
plier fabricated on an advanced, dielectrically isolated, comple-  
mentary bipolar process. In its basic mode, it provides the linear  
product of its X and Y voltage inputs. In this mode, the –3 dB  
output voltage bandwidth is 250 MHz (a small signal rise time  
of 1 ns). Full-scale (–1 V to +1 V) rise/fall times are 2.5 ns (with  
the standard RL of 150 ) and the settling time to 0.1% under  
the same conditions is typically 20 ns.  
As in earlier multipliers from Analog Devices, a unique sum-  
ming feature is provided at the Z-input. As well as providing in-  
dependent ground references for inputs and output, and  
enhanced versatility, this feature allows the AD835 to operate  
with voltage gain. Its X-, Y- and Z-input voltages are all nomi-  
nally ±1 V FS, with overrange of at least 20%. T he inputs are  
fully differential and at high impedance (100 kʈ2 pF) and pro-  
vide a 70 dB CMRR (f 1 MHz).  
Scaling Adjustm ent  
T he basic value of U in Equation 1 is nominally 1.05 V. Figure  
18, which shows the basic multiplier connections, also  
shows how the effective value of U can be adjusted to have any  
lower voltage (usually 1 V) through the use of a resistive-divider  
between W (Pin 5) and Z (Pin 4). Using the general resistor val-  
ues shown, we can rewrite Equation 1 as  
T he low impedance output is capable of driving loads as small  
as 25 . T he peak output can be as large as ±2.2 V minimum  
for RL = 150 , or ±2.0 V minimum into RL = 50 . T he  
AD835 has much lower noise than the AD534 or AD734, mak-  
ing it attractive in low level signal-processing applications, for  
example, as a wideband gain-control element or modulator.  
XY  
W =  
+ kW +(1 – k)Z '  
(3)  
U
(where Z' is distinguished from the signal Z at Pin 4). It follows  
that  
XY  
W =  
+ Z'  
(4)  
(5)  
(1 – k)U  
Basic Theor y  
In this way, we can modify the effective value of U to  
T he multiplier is based on a classic form, having a translinear  
core, supported by three (X, Y, Z) linearized voltage-to-current  
converters, and the load driving output amplifier. T he scaling  
voltage (the denominator U, in the equations below) is provided  
by a bandgap reference of novel design, optimized for ultralow  
noise. Figure 17 shows the functional block diagram.  
U ' = (1 – k)U  
without altering the scaling of the Z' input. (T his is to be ex-  
pected, since the only “ground reference” for the output is  
through the Z' input.)  
T hus, to set U' to 1 V, remembering that the basic value of U is  
1.05 V, we need to choose R1 to have a nominal value of 20  
times R2. T he values shown here allow U to be adjusted  
through the nominal range 0.95 V to 1.05 V, that is, R2 pro-  
vides a 5% gain adjustment.  
In general terms, the AD835 provides the function  
(X 1 – X 2)(Y1 – Y 2)  
(1)  
W =  
+ Z  
U
where the variables W, U, X, Y and Z are all voltages. Con-  
nected as a simple multiplier, with X = X1 – X2, Y = Y1 – Y2  
and Z = 0, and with a scale factor adjustment (see below) which  
sets U = 1 V, the output can be expressed as  
+5+V5V  
FB  
4.7µF TANTALUM  
(2)  
W = XY  
0.01µF CERAMIC  
X
W
7
8
6
5
X1  
X2  
VP  
W
X = X1 –X2  
XY  
X1  
X2  
AD835  
R1 = (1–k) R  
2kΩ  
AD835  
Y2  
Y1  
1
VN  
Z
4
2
3
XY + Z  
+1  
W OUTPUT  
Y
R2 = kR  
200Ω  
Y1  
Y2  
4.7µF TANTALUM  
0.01µF CERAMIC  
Y = Y1 –Y2  
1
Z
FB  
Z INPUT  
–5V  
Figure 17. Functional Block Diagram  
Figure 18. Multiplier Connections  
Note that in many applications, the exact gain of the multiplier  
may not be very important; in which case, this network may be  
omitted entirely, or R2 fixed at 100 .  
–6–  
REV. A  
AD835  
AP P LICATIO NS  
T he AD835 is both easy to use and versatile. T he capability for  
adding another signal to the output at the Z input is frequently  
valuable. T hree applications of this feature are presented here: a  
wideband voltage controlled amplifier, an amplitude modulator  
and a frequency doubler. Of course, the AD835 may also be  
used as a square law detector (with its X- and Y-inputs con-  
nected in parallel) in which mode it is useful at input frequen-  
cies to well over 250 MHz, since that is the bandwidth  
limitation only of the output amplifier.  
12dB  
(VG = 1V)  
6dB  
(VG = 0.5V)  
0dB  
(VG = 0.25V)  
Multiplier Connections  
Figure 18 shows the basic connections for multiplication. T he  
inputs will often be single sided, in which case the X2 and Y2  
inputs will normally be grounded. Note that by assigning Pins 7  
and 2 to these (inverting) inputs, respectively, an extra measure  
of isolation between inputs and output is provided. T he X and  
Y inputs may, of course, be reversed to achieve some desired  
overall sign with inputs of a particular polarity, or they may be  
driven fully differentially.  
10k  
100k  
1M  
10M  
100M  
START 10 000.000Hz  
STOP 100 000 000.000Hz  
Figure 20. AC Response of VCA  
An Am plitude Modulator  
Figure 21 shows a simple modulator. T he carrier is applied both  
to the Y-input and the Z-input, while the modulating signal is  
applied to the X-input. For zero modulation, there is no product  
term, so the carrier input is simply replicated at unity gain by  
the voltage follower action from the Z-input. At X = 1 V, the  
RF output is doubled, while for X = –1 V, it is fully suppressed.  
T hat is, an X-input of approximately ±1 V (actually ±U, or  
about 1.05 V) corresponds to a modulation index of 100%. Car-  
rier and modulation frequencies can be up to 300 MHz, some-  
what beyond the nominal –3 dB bandwidth.  
Power supply decoupling and careful board layout are always  
important in applying wideband circuits. T he decoupling rec-  
ommendations shown in Figure 18 should be followed closely.  
In remaining figures in this data sheet, these power supply  
decoupling components have been omitted for clarity, but  
should be used wherever optimal performance with high speed  
inputs is required. However, they may be omitted if the full high  
frequency capabilities of AD835 are not being exploited.  
A Wideband Voltage Contr olled Am plifier  
Figure 19 shows the AD835 configured to provide a gain of  
nominally 0 to 12 dB. (In fact, the control range extends from  
well under –12 dB to about +14 dB.) R1 and R2 set the gain to  
be nominally ×4. T he attendant bandwidth reduction that  
comes with this increased gain can be partially offset by the ad-  
dition of the peaking capacitor C1. Although this circuit shows  
the use of dual supplies, the AD835 can operate from a single  
9 V supply with slight revision.  
Of course, a suppressed carrier modulator can be implemented  
by omitting the feedforward to the Z-input, grounding that pin  
instead.  
+5V  
MODULATED  
MODULATION  
CARRIER  
INPUT  
OUTPUT  
8
7
6
5
X1  
X2  
VP  
W
AD835  
Y1  
1
Y2  
VN  
Z
4
+5V  
2
3
VG  
VOLTAGE  
OUTPUT  
(GAIN CONTROL)  
–5V  
CARRIER  
OUTPUT  
8
7
6
5
R1  
97.6  
X1  
X2  
VP  
W
AD835  
C1  
33pF  
Y1  
1
Y2  
VN  
Z
4
2
3
Figure 21. Sim ple Am plitude Modulator Using the AD835  
VIN  
(SIGNAL)  
Squar ing and Fr equency D oubling  
R2  
301Ω  
Amplitude domain squaring of an input signal, E, is achieved  
simply by connecting the X- and Y-inputs in parallel to pro-  
duce an output of E2/U. T he input may have either polarity, but  
the output in this case will always be positive. T he output polar-  
ity may be reversed by interchanging either the X or Y inputs.  
–5V  
Figure 19. Voltage Controlled 50 MHz Am plifier Using the  
AD835  
When the input is a sine wave E sin ωt, a signal squarer behaves  
as a frequency doubler, since  
T he ac response of this amplifier for gains of 0 dB (VG  
=
2
)
E2  
2U  
E sin ωt  
(
0.25 V), 6 dB (VG = 0.5 V) and 12 dB (VG = 1 V) is shown in  
Figure 20. In this application, the resistor values have been  
slightly adjusted to reflect the nominal value of U = 1.05 V. T he  
overall sign of the gain may be controlled by the sign of VG.  
(6)  
=
(1 – cos 2 ωt)  
U
While useful, Equation 6 shows a dc term at the output which  
will vary strongly with the amplitude of the input, E.  
REV. A  
–7–  
AD835  
Figure 22 shows a frequency doubler which overcomes this limi-  
tation and provides a relatively constant output over a moder-  
ately wide frequency range, determined by the time-constant C1  
and R1. T he voltage applied to the X- and Y-inputs are exactly  
in quadrature at a frequency f = 1/2 πC1R1 and their ampli-  
tudes are equal. At higher frequencies, the X-input becomes  
smaller while the Y-input increases in amplitude; the opposite  
happens at lower frequencies. T he result is a double frequency  
output, centered on ground, whose amplitude of 1 V for a 1 V  
input varies by only 0.5% over a frequency range of ±10%. Be-  
cause there is no “squared” dc component at the output, sud-  
den changes in the input amplitude do not cause a “bounce” in  
the dc level.  
O UTLINE D IMENSIO NS  
D imensions shown in inches and (mm).  
8-P in P lastic D IP  
(N P ackage)  
8
5
0.280 (7.11)  
0.240 (6.10)  
PIN 1  
1
4
0.325 (8.25)  
0.300 (7.62)  
0.430 (10.92)  
0.348 (8.84)  
0.060 (1.52)  
0.015 (0.38)  
0.195 (4.95)  
0.115 (2.93)  
0.210  
(5.33)  
MAX  
VG  
+5V  
0.130  
(3.30)  
MIN  
C1  
0.015 (0.381)  
0.008 (0.204)  
0.160 (4.06)  
0.115 (2.93)  
VOLTAGE  
OUTPUT  
8
7
6
5
SEATING  
PLANE  
0.100  
(2.54)  
0.070 (1.77)  
0.045 (1.15)  
0.022 (0.558)  
0.014 (0.356)  
X1  
X2  
VP  
W
R2  
97.6Ω  
BSC  
AD835  
Y2  
Y1  
1
VN  
Z
4
2
3
8-P in P lastic SO IC  
(R P ackage)  
R3  
301Ω  
R1  
–5V  
5
8
0.1574 (4.00)  
0.1497 (3.80)  
Figure 22. Broadband “Zero-Bounce” Frequency Doubler  
PIN 1  
0.2440 (6.20)  
4
T his circuit is based on the identity  
1
0.2284 (5.80)  
1
2
cos θ sin θ = sin 2θ  
( 7)  
0.1968 (5.00)  
0.1890 (4.80)  
0.0196 (0.50)  
x 45  
°
0.0099 (0.25)  
0.102 (2.59)  
0.094 (2.39)  
At ωO = 1/C1R1, the X input leads the input signal by 45° (and  
is attenuated by 2, while the Y input lags the input signal by  
45°, and is also attenuated by 2. Since the X and Y inputs are  
90° out of phase, the response of the circuit will be  
0.0098 (0.25)  
0.0040 (0.10)  
8
0
°
°
0.0500 (1.27)  
0.0160 (0.41)  
0.0500 0.0192 (0.49)  
0.0098 (0.25)  
0.0075 (0.19)  
(1.27)  
BSC  
0.0138 (0.35)  
1 E  
E
E2  
2U  
W =  
(sin ωt – 45° )  
(sin ωt + 45° ) =  
(sin 2ωt)  
( 8 )  
U
2
2
which has no dc component, R2 and R3 are included to restore  
the output to 1 V for an input amplitude of 1 V (the same gain  
adjustment as mentioned earlier). Because the voltage across the  
capacitor, C1, decreases with frequency, while that across the  
resistor, R1, increases, the amplitude of the output varies only  
slightly with frequency. In fact, it is only 0.5% below its full  
value (at its center frequency ωΟ = 1/C1R1) at 90% and 110%  
of this frequency.  
–8–  
REV. A  

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