OP-160_15 Datasheet, PDF (10/24 Pages) Analog Devices – High-Speed, Current Feedback Operational Amplifier

- ANALOGDEVICESfAX-ON-DEHANDHOTLINE Page 11
OP-160
TYPICAL PERFORMANCE CHARACTERISTICS Continued
NONINVERTING INPUT
BIAS CURRENT vs
POWER SUPPLY REJECTION
COMMON-MODE REJECTION
.- ^{COMMON-MODE VOLTAGE}
<' 1200
vs FREQUENCY
100
vs FREQUENCY
90
S
~_Ua:J
1000
800
TA=+25'C
Vs= i15V
§ ^--. 600
" <J')
'" _{~ 400}
II]
" _{"" 5 200}
CL
" ^~"
0
z -200
;::
""""
1>5 -400
~z -600
~-800
-20 -15 -10 -5 0 5 10 15 20
COMMON.MODEVOLTAGE(VOLTS)
"'-
z
80
0
;::
(w.wa,):
60
CL
C_:(:/)L_J
40
cwr
3: 20
0Q.
TA = +2S"C
RF = 820n
a
lk
10k
lOOk 1M
FREQUENCY(Hz)
00 ⁸⁰
E
;Z
0
70
j::
w(w.,)
a:
60
50
wa
0
40
z 30
0
::i: ₂₀
() 10
0
10M
100
TA= +25"C
RF= 820n
Vs =.t15V
lk
10k lOOk 1M
10M
FREQUENCY (Hz)
OB _{APPLICATIONS INFORMATION}
CURRENT VERSUS VOLTAGE FEEDBACK AMPLIFIERS
S _{The OP-160 employs a unique circuit topology that sets it apart}
O ^{from conventional op amps. By using a transimpedance ampli-}
fier configuration, the OP-160 provides substantial improve-
L ^{ments in bandwidth and slew rate over voltage feedback op}
amps. Figure 1 compares models of these two different ampli-
E _{fier configurations.}
TE _{A voltage feedback op amp multiplies the differential voltage at}
high impedance inputs, the current feedback amplifier has a
high and a low impedance input. The current feedback
amplifier's input stage consists of a unity-gain voltage buffer
between the noninverting and inverting inputs. The inverting
"input" is in reality a low impedance output. Current can flow into
or out of the inverting input. A transimpedance stage follows the
input buffer that converts the buffer output current into a linearly
proportional amplifier output voltage.
its inputs by its open-loop gain. The feedback loop forces the
The current feedback amplifier loop works in the following fash-
output to a voltage that, when divided by R, and Rz' equalizes
the input voltages. Unlike a voltage feedbackopamp, which has
ion (Figure 1b). As the non inverting input voltage rises, the in-
verting input follows and the buffer sources current through R,"
CONVENTIONAL OP AMP
a)
VIN
VOlIr
CURRENT FEEDBACK OP AMP
b)
vll'~
VOUT
RZ
A,
-;-
AV-l~
VOLTAGE-GONTAOLLED
VOLTAGE SOURCE
R2
R,
-
R2
-
AV=1+R;
CURRENT-CONTROLLED
VOLTAGE SOURCE
FIGURE 1: The conventional op amp (a) can be modelled as a voltage-controlled voltage source. In contrast, the current feedback
op amp (b), resembles a current-controlled voltage source.
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