AB-180 [ETC]
AB-180 - ULTRA HIGH-SPEED ICs ; AB - 180 - 超高速集成电路\n
| 型号： | AB-180 |
| 厂家： | 
ETC |
| 描述： | AB-180 - ULTRA HIGH-SPEED ICs
|
| 文件： | 总5页 (文件大小：92K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
®
AP P LICATION BULLETIN
Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Tel: (602) 746-1111 • Twx: 910-952-111 • Telex: 066-6491 • FAX (602) 889-1510 • Immediate Product Info: (800) 548-6132
ULTRA HIGH-SPEED ICs
By Klaus Lehmann, Burr-Brown International GmbH
1
2
3
OPA660 Current
Feedback Amplifier
OPA622 Voltage
Feedback Amplifier
OPA660 Straight
Foward Amplifier
Out
Out
+In
–In
Out
+In
+In
4
5
QUASI-IDEAL CURRENT SOURCE
6
In addition to their actual operation parameter
transconductance, active electronic key components such as
vacuum tubes, field effect transistors, and bipolar transistors
demonstrate diverse negative parameters. In applying the so-
called Diamond structure, the user can obtain an improved
current source with reduced disturbance parameters, as well
as a programmable transconductance independent of tem-
perature. Standard applications for the Diamond current
source (DCS) can be found in buffers, operational amplifiers
with voltage or current feedback, and transconductance
amplifiers. The DCS simplifies the design of electronic
circuits with bandwidths of up to 400MHz and slew rates of
3000V/µs with a low supply current of several mA.
COMPONENT
PARAMETER
TYPICAL VALUE
Triode
Grid Bias Voltage
Anode Bias Voltage
Grid Current
Anode Bias Current
G/K Resistance
A/K Resistance
0 to 10V
20 to 1kV
nA to µA
µA to A
kΩ to MΩ
kΩ to MΩ
1 to 20%
Trans Grid Action
N-J FET
Gate Voltage
D/S Voltage
Gate Current
0 to –10V
0 to 100V
fA to µA
D Bias Current
G/S Resistance
D/S Resistance
Inverse Amplification
µA to A
MΩ to GΩ
kΩ to MΩ
1 to10%
NPN Transistor
Basis Voltage
K/E Voltage
Basis Current
0.5 to 0.8V
0.5 to 100V
µA to mA
µA to A
kΩ
VOLTAGE-CONTROLLED CURRENT SOURCES
K Bias Current
B/E Resistance
K/E Resistance
Inverse Amplification
For analog signal processing, especially current or voltage
gain, previous electronic circuit techniques primarily used
vacuum tubes, while today they use field effect or bipolar
transistors. The triode illustrated in Figure 1 is representa-
tive of the various vacuum tubes, while the N-channel FET
represents the FET variations (junctions, insulated gates,
depletion, enhancements, P-channels, and N-channels), and
a NPN transistor represents the range of bipolar transistors.
Triodes, N-J FETs, and NPN transistors are compared with
the Diamond current source (DCS). The common elements
of all of these active elements are a relatively high-imped-
ance input electrode 1 (grid, gate, basis), a low-impedance
kΩ
0.1 to 1%
DCS
VOFF1
VOFF3
IBIAS1
IBIAS3
R12
–2 to +2mV
0V
nA to µA
µA
kΩ to MΩ
kΩ
<0.1%
R32
VR31
TABLE I. Typical Disturbance Parameters of the Voltage-
Controlled Current Sources.
©1993 Burr-Brown Corporation
AB-180
Printed in U.S.A. May, 1993
input and output electrode 2 (cathode, source, emitter), and
a high-impedance output electrode 3 (anode, drain collec-
tor). Thus all of these elements can be treated as special
voltage-controlled current sources (VCCS = Voltage-Con-
trolled Current Source). The limitation “special” refers to
the low-impedance input and output electrode 2. The most
important relation between the electrodes 1, 2, and 3 is the
transconductance gm. For instance, the transconductance
describes the change of the output signal (VOUT) dependent
upon the input signal (VIN).
VOUT = VIN x gm x ROUT (1)
To operate each VCCS, it is necessary to adjust the DC
quiescent current or voltage individually (see Figure 1).
Triade
N - J - FET
NPN - Transistor
DCS
3
2
3
2
3
2
3
2
A
K
D
C
1
1
1
1
–gm
–gm
–gm
–gm
G
G
B
gm
E
Vbc
Vbe
V
be /VT
V
be /VT
Vgk < Ø (Vgk + DVak) > Ø
I
d = βVds (1 + λVds) [2 (Vgs – Vβ ) – Vgs
]
Ic = Is (1 –
–
) (e
– e
)
I3 = V12 x gm
Ig
VAF VAR
Is
3
/
2
2
Ia = K (Vgk + DVak
)
I
d = β (1 + λVds) (Vgs – Vp
)
dTc
gm = 2K
Vbe /VT
e
VT
gm =
=
dVbe VT
dIa
3
2
dId
K = 0.81; VT = 25.9mV
gm =
+
K
Vgk + DVak
gm =
= 2β (1 + λVgs) (Vgs – Vp )
dVgk
dVgs
Is = 1.58E –16; VAF = 66; VAR = 3
K = 0.001; D = 0.05
β = 2.258E –3; λ = 21.31E–3; Vp = –2
+I3
(mA)
(mA) Ic
10
(mA) Ia
(mA) Id
Vgk
–1V
–2V
–3V
–4V
–5V
30
25
20
15
10
5
10
+60mV
+40mV
+20mV
+10
Vbe
Vgs
V12
0.828V
0.822V
0.815V
0.804V
±ØV
8
8
6
4
2
+5
–V32
+V32
–Ø.21V
6
–Ø.45V
4
–Ø.73V
2
–3 –2 –1
+1 +2 +3
–20mV
(V)
(V)
–5
–40mV
Vak
Vds
Vce
5
0.786V
3 4
–1.1V
–10
–60mV
(mA)
(V)
1
2
(V)
(V)
–I3
50 100 150 200
1
2
3
4
5
+I3
(mA)
(mA)
Ic
(mA)
12
10
8
(mA)
Ia
Id
Ig
Vak
+10
+5
10
10
8
Vds
2.4mA
Vce
1.2mA
0.6mA
0.3mA
8
6
4
2
60V
1V...5V
40V
20V
+5V
–V12
–60 –40 –20
6
6
+V12
80V
100V
+20 +40 +60
(mV)
(mV)
4
4
–5
+2.5V
2
2
Vbe
–Vgk
–Vgs
–10
–I3
(mA)
(V)
0.2 0.4 0.6 0.8
1
(V)
(V)
–5 –4 –3 –2 –1
–2 –1.5 –1 –0.5
(gm)
(mA/V)
(mA/V)
(mA/V)
(mA/V)
gm
gm
40V
gm
Ig
160
120
80
Vak
5V
3V
1V
Vds
+5V
400
300
200
100
4
3
2
1
10
8
Vce
2.4mA
1.2mA
60V
6
+2.5V
80V
4
0.6mA
0.3mA
100V
40
2
Vbe
(V)
–Vgk
–Vgs
(V)
–V12
(mV)
+V12
(mV)
20 40 60
20V
–5 –4 –3 –2 –1
–
+
0.72
0.76 0.80 0.84
60 40 20
(V)
–2 –1.5 –1 –0.5
FIGURE 1. Comparison Between Voltage-Controlled Current Source (VCCS) and Diamond Current Source (DCS).
2
Real VCCS
Ideal VCCS
Input
Signal
Input
Compensation
Output
Compensation
Output
Signal
VOUT
3
–
+
+ –
3'
VOFF1
V'OFF1
V'r31
V'OFF3
VOFF3
1
1'
–
+
+
+ –
gm
R'32
RL
2'
I'BIAS3
IBIAS3
VIN
R'12
R'S
1
/
IBIAS1
I'BIAS1
gm
2
FIGURE 2. Internal and External Substitute Circuitry of a Voltage-Controlled Current Source.
Figure 2 illustrates the inner and outer substitute circuitry of
a voltage-controlled current source VCCS. According to the
circuitry, the VCCS (1, 2, 3) consists of an inner ideal VCCS
(1', 2', 3') with transconductance gm and a row of inner
disturbance parameters (V', I' , R'), which determine, among
other things, the adjustment of the DC point. Table I shows
a rough overview of the disturbance parameters. Almost all
disturbance parameters are subject to tolerances between
units and show dependent temperature behavior.
mond circuit, illustrated in Figure 4, opens up the possibility
of implementing the quasi-ideal VCCS [2]. In the ideal case,
in which NPN and PNP transistors are identical, the distur-
bance parameters V0FF1', VOFF3', IBIAS1', and IBIAS3' disappear.
But in real circuits, of course, this is not the case. The
remaining parameter values are, however, much smaller in
comparison with a conventional VCCS (compare VCCS
with DCS in Figure 1 and Table I). In the modulation range
being examined, from I3 = ±10mA, the transconductance
varies from 120 to 160mA/V as opposed to 0 to 350mA/V.
This means that the improved VCCS (designated DCS from
now on) causes a reduction in signal distortion.
Figure 2 also illustrates the correction parameters (VOFF1
,
VOFF3, IBIAS1, and IBIAS3), which are required primarily to
compensate the internal disturbance parameters. The correc-
tion parameters, however, do not correct the effects of the
internal disturbance parameters (R'12, R'32) and the output
voltage feed-through V'r31. Roughly stated, at least 50% of
the design time for electronic circuit techniques goes toward
dealing with the problem of compensation. Thus in complex
circuits, the connection between the function parameter gm
and the various disturbance parameters requires more and
more modifications in circuit variations. If a VCCS without
disturbance parameters was available for users, the huge
variety of electronic circuit techniques could be reduced.
1
VIN
3
OTA
B
2
VOUT
R2
Rf
FIGURE 3. Operational Amplifiers as Series Connection
Between OTA and Buffer.
THE “IDEAL” CURRENT SOURCE
The macro element operational transconductance amplifier
(OTA) and operational amplifier (OA) contain circuit parts
for reducing the previously mentioned disturbance param-
eters. The feedback operation necessary with these amplifi-
ers— i.e. the application of a control loop with its unavoid-
able delay time (phase delays)— causes significantly re-
duced time and frequency domain performance compared to
the VCCS. Straight-forward amplifiers are thus more wide-
banded than feedback amplifiers. An operational amplifier
OA, as shown in Figure 3, consists of the series connection
of an OTA with a buffer B. The OTA is a voltage-controlled
current source VCCS, in which the electrode 2 can be used
“only” as a high-impedance input. Because of this distinc-
tion, the OTA can only be used with an external feedback
loop. In contrast to conventional operational amplifiers with
voltage feedback as shown in Figure 3, the current-feedback
OA contains an OTA with low-impedance input and output
2—i.e. the previously represented “ideal” VCCS. The Dia-
VCC
I'Q
3
3
IO
1
2
3
1
1
/
/
6
6
IO
3
3
I'Q
VEE
FIGURE 4. VCCS with Diamond Structure.
3
PROGRAMMABLE TRANSCONDUCTANCE
are available for the DCS (Figure 7): Buffer (B), Current-
Feedback Transconductance Buffer (TB), Transconductance
Amplifier (TA), Direct-Feedback Transconductance
Amplifier (TD), Current-Feedback OA (TCC), and Voltage-
Feedback OA (TCV).
Conventional VCCSs allow the transconductance to be
adjusted depending upon the quiescent current. In the DCS,
the transconductance is adjusted primarily with the current
sources I'Q (see Figure 4). For this adjustment, one effective
method is to create a current source control (Figure 5).
OUTLOOK
Using the resistor RQ, the quiescent current I'Q or IQ and thus
the transconductance gm can be fixed. The temperature
function of gm (due to VT = f(T)) is compensated for by
corresponding variations of IQ. For RQ → ∞, IQ → 0 and gm
→ 0, and VCCS is switched off. In contrast to the conven-
tional VCCS, the DCS functions in two quadrants at the
input and in four at the output. In the VCCS, the
transconductance is fixed by the choice of DC points within
the usable modulation range, while the transconductance in
the DCS is largely independent of the modulation and can be
adjusted with the external resistor RQ.
To characterize typical dynamic coefficient values (Table
II), a developed DCS including a SOI package was simu-
lated in the circuit shown in Figure 8. Burr-Brown brought
this DCS onto the market as OPA660.
LITERATURE
[1] Ross, D.G. et al; IEEE Journal of solid-state circuits
86, vol. 2, p. 331.
[2] Lehmann, K; Elektronik Industrie 89, vol. 5, p. 99.
Strom-oder Spannungs-Gegenkopplung?
(Current or Voltage Feedback? That’s the question
here.)
gm = dI3/dV12 is negative for all VCCSs. In contrast, the
transconductance gm = dI3/dV12 of the DCS is positive. As
previously mentioned, the following standard applications
VCC
3
VT
1
1
1
1
1
VIN
I'Ø
=
In (1Ø)
+gm
+gm
RØ
2
2
I'O
2KIØ 2K X 18I'Ø
=
RIN
ROUT2
gm =
gm =
I'O
I'O
VOUT
VT
VT
I'O
2K X 18 X In (10)
RØ
10
FIGURE 8. Circuit for Recording the Dynamic Charac-
teristic of a TCC with DCS.
1
1
RQ
VEE
0.1Vp-p
f–3dB
6Vp-p
f–3dB
4Vp-p
SR
1.4Vp-o
DG
5MHz
DP
FIGURE 5. Current Source Control with Adjustable Bias
Current.
IQ
(mA)
(MHz)
(MHz)
(V/µs)
(%)
(Degrees)
2.4
1.2
0.6
0.3
400
240
140
80
330
200
100
55
2850
1750
800
–0.07
–0.06
–0.05
–0.03
–0.05
–0.06
–0.10
–0.19
+V
4
420
3
TABLE II. Typical Dynamic Values of a TCC with DCS
Corresponding to the Circuit in Figure 8.
1
+gm
(mA/V)
2
1000
100
5
6
RQ
–V
(gm)
10
1
RQ
0.1
1
10
(Ω)
FIGURE 6. The Relations gm = f(RQ) and Block Diagram of
the DCS.
4
B
TB
3
VB = 1/[1 + 1/(gm x RIN)] = 1
Ri2 = 1/gm
3
1
1
1
1
VIN
VIN
+gm
+gm
+gm
+gm
+gm
ROUT
VTB = 1/[1 + 1/(2gm x RIN)] = 1
2
2
RIN
RIN
Ri2 = 1/2gm
V'OUT
VOUT
TA
3
TA
3
V'OUT
VOUT
+VTA = ROUT/(RIN + 1/gm) = ROUT/RIN
+Ri3 = ROUT
1
ROUT
ROUT
VIN
–VTA = +VTA
2
2
RIN
RIN
–Ri3 = ROUT
VIN
ROUT/2 + RIN
RIN + 1/(2gm)
ROUT
2RIN
TC
TC
3
+VTC
=
=
= 1 +
VOUT
VOUT
3
1
ROUT/2 – 1/(2gm)
RIN + 1/(2gm)
ROUT
VIN
+gm
ROUT
–VTC
= –
2RIN
2
2
RIN
RIN
ROUT
2
RIN (ROUT/2 – 1/(2gm)
VIN
Ri3 = ROUT
–
=
RIN + 1/(2gm)
TCC
3
TCC
3
ROUT
RIN
+VTCC = 1 +
1
1
1
1
VIN
+gm
+gm
+gm
+gm
ROUT
2
2
2
2
–VTCC = –
RIN
ROUT
RIN
ROUT
RIN
VOUT
VIN
VOUT
TCV
TCV
1
1
+gm
+gm
3
2
3
+gm
ROG
2
+gm
3
ROUT
ROUT
RIN
1
1
1
1
+VTCV = 1 +
VIN
VOUT
2
2
2
RIN
ROG
ROUT
–VTCV = –
RIN
RIN
ROUT
VOUT
VIN
FIGURE 7. Standard Applications with the DCS.
5
相关型号：
©2020 ICPDF网 联系我们和版权申明