OPA328 datasheet(17/23 Pages) TI

17 / 23 page

The key elements to a transimpedance design, as shown in Figure 8-4, are the:

• Expected diode capacitance (CD), which should include the parasitic input common-mode voltage and

differential-mode input capacitance

• Desired transimpedance gain (RF)

• Gain-bandwidth (GBW) for the OPAx328 (40 MHz)

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

CF includes the stray capacitance of RF, which is 0.2 pF for a typical surface-mount resistor.

–

V+

Amp

VOUT

10 M

V–

NOTE: CF is optional to prevent gain peaking, and includes the stray capacitance of RF.

Figure 8-4. Dual-Supply Transimpedance Amplifier

For optimal frequency response, set the feedback pole as shown in Equation 6:

2 R C

4 R C

GBW

(6)

Bandwidth is calculated by Equation 7:

3dB =

2 R C

GBW

(Hz)

(7)

For single-supply applications, the +IN input can be biased with a positive dc voltage to allow the output to reach

true zero when the photodiode is not exposed to any light, and respond without the added delay that results from

coming out of the negative rail. This configuration is shown in Figure 8-5. This bias voltage also appears across

the photodiode, providing a reverse bias for faster operation.

–

V+

Amp

VOUT

10 M

VBIAS

NOTE: CF is optional to prevent gain peaking, and includes the stray capacitance of RF.

Figure 8-5. Single-Supply Transimpedance Amplifier

For additional information, see the Compensate Transimpedance Amplifiers Intuitively application report,

available for download at www.ti.com.

www.ti.com

OPA2328

SBOS957 – FEBRUARY 2022

Submit Document Feedback

Product Folder Links: OPA2328

OPA328 Datasheet(PDF) 17 Page - Texas Instruments

OPA328 Datasheet(HTML) 17 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Datasheet Download

Link URL