10k

100k

1M

10M

FREQUENCY (Hz)

50

55

60

65

70

75

80

85

90

95

100

10k

100k

1M

10M

FREQUENCY (Hz)

50

60

70

80

90

100

110

120

130

LMV796, LMV797

www.ti.com

SNOSAU9D – MARCH 2006 – REVISED MARCH 2013

HIGH GAIN WIDEBAND TRANSIMPEDANCE AMPLIFIER USING THE LMV797

The LMV797 dual, low noise, wide bandwidth, CMOS input op amp IC can be used for compact, robust and

integrated solutions for sensing and amplifying wide-band signals obtained from sensitive photodiodes. One of

the two op amps available can be used to obtain transimpedance gain while the other can be used for amplifying

the output voltage to further enhance the transimpedance gain. The wide bandwidth of the op amps (17 MHz)

ensures that they are capable of providing high gain for a wide range of frequencies. The low input referred noise

(5.8 nV/

√Hz) allows the amplifier to deliver an output with a high SNR (signal to noise ratio). The small 8-pin

VSSOP footprint saves space on printed circuit boards and allows ease of design in portable products.

The circuit shown in Figure 57, has the first op amp acting as a transimpedance amplifier with a gain of 47000,

while the second stage provides a voltage gain of 10. This provides a total transimpedance gain of 470000 with a

−3 dB bandwidth of about 1.5 MHz, for a total input capacitance of 50 pF. The frequency response for the circuit

is shown in Figure 58

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