OPA320-Q1

V

O

V

(V+)

V

(V–)

C

(D)

R

10 MΩ

(F)

C

< 1 pF

(F)

(1)

l

17

OPA320-Q1, OPA2320-Q1

www.ti.com

SLOS884B – SEPTEMBER 2014 – REVISED DECEMBER 2018

Product Folder Links: OPA320-Q1 OPA2320-Q1

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Copyright © 2014–2018, Texas Instruments Incorporated

8 Application and Implementation

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.

8.1 Application Information

The OPAx320-Q1 can be used in a wide range of applications, such as transimpedance amplifiers, high-

impedance sensors, active filters, and driving ADCs.

8.2 Typical Applications

8.2.1 Transimpedance Amplifier

Wide gain bandwidth, low input bias current, low input voltage, and current noise make the OPAx320-Q1 an

excellent wideband photodiode transimpedance amplifier. Low-voltage noise is important because photodiode

capacitance causes the effective noise gain of the circuit to increase at high frequency.

The key elements to a transimpedance design, as shown in Figure 36, are the expected diode capacitance

(C(D)), which should include the parasitic input common-mode and differential-mode input capacitance (4 pF + 5

pF); the desired transimpedance gain (R(FB)); and the gain-bandwidth (GBW) for the OPAx320-Q1 (20 MHz).

With these three variables set, the feedback capacitor value (C(FB)) can be set to control the frequency response.

C(FB) includes the stray capacitance of R(FB), which is 0.2 pF for a typical surface-mount resistor.

(1) C(FB) is optional to prevent gain peaking. C(FB) includes the stray capacitance of R(FB).

Figure 36. Dual-Supply Transimpedance Amplifier

8.2.1.1 Design Requirements

PARAMETER

VALUE

Supply voltage V(V+)

2.5 V

Supply voltage V(V–)

–2.5 V