8.2.1.3 Application Curves

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

-6

-4.5

-3

-1.5

0

1.5

3

4.5

6

D100

Figure 8-3. DC Transfer Characteristics

Time, 250 ns per division

-5.5

-4.5

-3.5

-2.5

-1.5

-0.5

0.5

1.5

2.5

3.5

4.5

5.5

D100

Figure 8-4. Transient Output Response

8.2.2 Transimpedance Amplifier Configuration

With recent advancements in light-sensing technology, transimpedance (TIA) applications are becoming popular,

ranging in signal bandwidth needs from tens of kHz to hundreds of MHz. Because the current output of the

photodiode in these TIA applications is unipolar, a key challenge in interfacing with the fully differential input

analog-to-digital converters (ADCs) is maximizing the differential signal to the ADC in order to maximize the

signal-to-noise ratio (SNR).

As illustrated in the output waveform of Figure 8-6, only half the differential output signal swing of the FDA is

available. On the contrary, by using the OPA862 as the TIA stage, a single-device interface to the ADC can be

designed that also allows the full differential swing to the ADC and set the desired output common-mode as

R

F

C

F

V

BIAS

A1

+

±

A2

+

±

700

700

OPA862

R

INT

R

INT

V

OUT+

V

OUT±

V

REF

V

DC

V

REF

V

OUT±

V

OUT+

Figure 8-5. Improved TIA Signal Chain With the OPA862

www.ti.com

OPA862

SBOS919C – AUGUST 2019 – REVISED AUGUST 2020

Copyright © 2020 Texas Instruments Incorporated

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