OPA1641-Q1 Datasheet, PDF (18/31 Pages) Texas Instruments – SoundPlus JFET-Input, Automotive-Grade, Audio Operational Amplifiers

OPA1641-Q1, OPA1642-Q1
SBOS791 – JUNE 2017
www.ti.com
7.5
7
Traditional JFET-Input Amplifier
6.5
6
OPA164x Family
5.5
5
4.5
4
–10 –8 –6 –4 –2 0 2 4 6
Common-Mode Voltage (V)
8 10
Figure 34. Input Capacitance of the OPA164x-Q1 Family of Amplifiers Compared to Traditional JFET-
input Amplifiers
By stabilizing the input capacitance, the distortion performance of the amplifier is greatly improved for
noninverting configurations with high source impedances. The measured performance of an OPA164x-Q1
amplifier is compared to a traditional JFET-input amplifier in Figure 35. The unity-gain configuration, high source
impedance, and large-signal amplitude produce additional distortion in the traditional amplifier.
1%
10 kΩ
+
–
5 VRMS
0.1%
–40
–50
–60
–70
Traditional JFET-Input Amplifier
0.01%
–80
0.001%
–90
OPA164x Amplifier _–100
–110
0.0001%
10
100
1k
Frequency (Hz)
–120
10k 20k
Figure 35. Measured THD+N of the OPA164x-Q1 Family of Amplifiers Compared to Traditional JFET-
input Amplifiers
8.1.3 Capacitive Load and Stability
The dynamic characteristics of the OPA164x-Q1 are optimized for commonly encountered gains, loads, and
operating conditions. The combination of low closed-loop gain and high capacitive loads decreases the phase
margin of the amplifier and can lead to gain peaking or oscillations. As a result, heavier capacitive loads must be
isolated from the output. The simplest way to achieve this isolation is to add a small resistor (R_OUT equal to 50 Ω,
for example) in series with the output.
Figure 19 and Figure 20 illustrate graphs of Small-Signal Overshoot vs Capacitive Load for several values of
R_OUT. For details of analysis techniques and application circuits, see see Feedback Plots Define Op Amp AC
Performance available for download at www.ti.com
18
Submit Documentation Feedback
Copyright © 2017, Texas Instruments Incorporated
Product Folder Links: OPA1641-Q1 OPA1642-Q1