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