TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, and VS = ±15V, unless otherwise noted.
SETTLING TIME vs ERROR BAND
SETTLING TIME vs LOAD CAPACITANCE
1500
1000
500
0
3
2
1
0
CF
+5V
–5V
OPA627 OPA637
RI
RF
OPA637
G = –4
–
+
RI 2kΩ
RF 2kΩ
CF 6pF
500Ω
2kΩ
4pF
Error Band:
±0.01%
2kΩ
OPA627
G = –1
OPA627
G = –1
OPA637
G = –4
0.001
0.01
0.1
Error Band (%)
1
10
0
150
200
300
400
500
Load Capacitance (pF)
APPLICATIONS INFORMATION
RF < 4RI
OPA627
The OPA627 is unity-gain stable. The OPA637 may be used
to achieve higher speed and bandwidth in circuits with noise
gain greater than five. Noise gain refers to the closed-loop
gain of a circuit as if the non-inverting op amp input were
being driven. For example, the OPA637 may be used in a
non-inverting amplifier with gain greater than five, or an
inverting amplifier of gain greater than four.
OPA627
–
–
+
+
Buffer
Non-Inverting Amp
G < 5
RI
RF < 4R
RI
When choosing between the OPA627 or OPA637, it is
important to consider the high frequency noise gain of your
circuit configuration. Circuits with a feedback capacitor
(Figure 1) place the op amp in unity noise-gain at high
frequency. These applications must use the OPA627 for
proper stability. An exception is the circuit in Figure 2,
where a small feedback capacitance is used to compensate
for the input capacitance at the op amp’s inverting input. In
this case, the closed-loop noise gain remains constant with
frequency, so if the closed-loop gain is equal to five or
greater, the OPA637 may be used.
OPA627
OPA627
–
–
+
+
Bandwidth
Limiting
Inverting Amp
G < |–4|
OPA627
OPA627
–
–
+
+
Filter
Integrator
FIGURE 1. Circuits with Noise Gain Less than Five Require
the OPA627 for Proper Stability.
®
OPA627, 637
8
TI [ TEXAS INSTRUMENTS ]
