Datasheet

8
®
OPA627, 637
TYPICAL PERFORMANCE CURVES (CONT)
At T
A
= +25°C, and V
S
= ±15V, unless otherwise noted.
FIGURE 1. Circuits with Noise Gain Less than Five Require
the OPA627 for Proper Stability.
SETTLING TIME vs ERROR BAND
1500
1000
500
0
0.001 0.01 0.1 1 10
Error Band (%)
Settling Time (ns)
OPA637
G = –4
OPA627
G = –1
–
+
C
F
R
I
R
F
2kΩ
+5V
–5V
OPA627 OPA637
R
I
2kΩ 500Ω
R
F
2kΩ 2kΩ
C
F
6pF 4pF
SETTLING TIME vs LOAD CAPACITANCE
0 150 200 300 400 500
Load Capacitance (pF)
3
2
1
0
Settling Time (µs)
Error Band:
±0.01%
OPA637
G = –4
OPA627
G = –1
APPLICATIONS INFORMATION
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.
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.
–
+
–
+
–
+
–
+
–
+
–
+
Buffer
Bandwidth
Limiting
Integrator
Filter
R
I
R
F
< 4R
Inverting Amp
G < |–4|
R
I
R
F
< 4R
I
Non-Inverting Amp
G < 5
OPA627 OPA627
OPA627
OPA627
OPA627 OPA627