Texas Instruments | Transimpedance amplifier circuit. (Rev. A) | Application notes | Texas Instruments Transimpedance amplifier circuit. (Rev. A) Application notes

Texas Instruments Transimpedance amplifier circuit. (Rev. A) Application notes
Analog Engineer's Circuit: Amplifiers
SBOA268A – February 2018 – Revised January 2019
Transimpedance amplifier circuit
Design Goals
Input
Output
BW
Supply
IiMin
IiMax
VoMin
VoMax
fp
Vcc
Vee
0A
50µA
0V
5V
10kHz
15V
–15V
Design Description
The transimpedance op amp circuit configuration converts an input current source into an output voltage.
The current to voltage gain is based on the feedback resistance. The circuit is able to maintain a constant
voltage bias across the input source as the input current changes which benefits many sensors.
V+
C3 100n
C1 150p
C2 100n
Vcc 15
Vee 15
R1 100k
VIi
+ +
Vout
U1 OPA170
V+
V-
Copyright © 2018, Texas Instruments Incorporated
Design Notes
1. Use a JFET or CMOS input op amp with low bias current to reduce DC errors.
2. A bias voltage can be added to the non-inverting input to set the output voltage for 0-A input currents.
3. Operate within the linear output voltage swing (see Aol specification) to minimize non-linearity errors.
SBOA268A – February 2018 – Revised January 2019
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Copyright © 2018–2019, Texas Instruments Incorporated
Transimpedance amplifier circuit
1
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Design Steps
1. Select the gain resistor.
2. Select the feedback capacitor to meet the circuit bandwidth.
3. Calculate the necessary op amp gain bandwidth (GBW) for the circuit to be stable.
•
•
•
2
Cs: Input source capacitance
Cd: Differential input capacitance of the amplifier
Ccm: Common-mode input capacitance of the inverting input
Transimpedance amplifier circuit
SBOA268A – February 2018 – Revised January 2019
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Copyright © 2018–2019, Texas Instruments Incorporated
www.ti.com
Design Simulations
DC Simulation Results
AC Simulation Results
SBOA268A – February 2018 – Revised January 2019
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Transimpedance amplifier circuit
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Design References
See Analog Engineer's Circuit Cookbooks for TI's comprehensive circuit library.
See circuit SPICE simulation file SBOC501.
See TIPD176, www.ti.com/tool/tipd176.
Design Featured Op Amp
OPA170
Vcc
2.7V to 36V
VinCM
(Vee–0.1V) to (Vcc –2V)
Vout
Rail–to–rail
Vos
0.25mV
Iq
0.11mA
Ib
8pA
UGBW
1.2MHz
SR
0.4V/µs
#Channels
1, 2, 4
www.ti.com/product/opa170
Design Alternate Op Amp
OPA1671
Vcc
1.7V to 5.5V
VinCM
Rail–to–rail
Vout
(Vee+10mV) to (Vcc-10mV) @
275µA
Vos
250µV
Iq
940µA
Ib
1pA
UGBW
12MHz
SR
5V/µs
#Channels
1
www.ti.com/product/opa1671
Revision History
4
Revision
Date
A
January 2019
Transimpedance amplifier circuit
Change
Downscale the title and changed title role to 'Amplifiers'.
Updated Design Alternate Op Amp table with OPA1671.
Added link to circuit cookbook landing page.
SBOA268A – February 2018 – Revised January 2019
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Copyright © 2018–2019, Texas Instruments Incorporated
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