OPA2836-Q1 Datasheet, PDF (28/44 Pages) Texas Instruments – Very-Low Power, Rail-to-Rail Out, Negative-Rail In, Voltage-Feedback Operational Amplifier

OPA2836-Q1
SBOS794 – DECEMBER 2016
9 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
9.1.1 Noninverting Amplifier
The OPA2836-Q1 can be used as a noninverting amplifier with a signal input to the noninverting input, V_IN+ . A
basic block diagram of the circuit is illustrated in Figure 51.
If V_IN = V_REF + V_SIG, then the output of the amplifier can be calculated according to Equation 1.
æ
VOUT
=
V_SIG
ç¹
è
+
R_F
R_G
ö
÷
ø
+ V_REF
(1)
G = 1 + ^RF
The signal gain of the circuit is set by
R_{G , and VREF provides a reference around which the input and}
output signals swing. Output signals are in-phase with the input signals.
The OPA2836-Q1 is designed for the nominal value of R_F to be 1 kΩ in gains other than +1. This value gives
excellent distortion performance, maximum bandwidth, best flatness, and best pulse response. R_F = 1 kΩ must
be used as a default unless other design goals require changing to other values. All test circuits used to collect
data for this document have R_F = 1 kΩ for all gains other than +1. Gain of +1 is a special case where R_F is
shorted and R_G is left open.
9.1.2 Inverting Amplifier
The OPA2836-Q1 can be used as an inverting amplifier with a signal input to the inverting input, V_IN– , through
the gain setting resistor R_G. A basic block diagram of the circuit is illustrated in Figure 52.
If V_IN = V_REF + V_SIG, then the output of the amplifier may be calculated according to Equation 2.
VOUT
=
V_SIG
æ
ç
è
-R_F
R_G
ö
÷ ^{+ V}REF
ø
(2)
G = ^-RF
The signal gain of the circuit is set by:
R_{G , and VREF provides a reference point around which the input}
and output signals swing. Output signals are 180° out-of-phase with the input signals. The nominal value of R_F
must be 1 kΩ for inverting gains.
9.1.3 Instrumentation Amplifier
Figure 62 is an instrumentation amplifier that combines the high input impedance of the differential-to-differential
amplifier circuit and the common-mode rejection of the differential-to-single-ended amplifier circuit. This circuit is
often used in applications where high input impedance is required (such as taps from a differential line or in
cases where the signal source has a high output impedance).
If V_IN+ = V_CM + V_SIG+ and V_IN– = V_CM + V_SIG– , then the output of the amplifier can be calculated according to
Equation 3.
VOUT =
(V_IN+ - V_IN- )
´
æ
ç¹
è
+
2R_F1
ö
÷
R_{G1 ø}
æ
ç
è
R_F2
R_G2
ö
÷⁺
ø
V_REF
(3)
28
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