LMV793, LMV794

SNOSAX6D – MARCH 2007 – REVISED MARCH 2013

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Figure 54. RC = 330Ω and C = 10 nF, Gain = +1

Figure 55. LMV796 Response Gain = +1

With no increase in power consumption the decompensated op amp offers faster speed over the compensated

equivalent part. These examples used RF = 2 kΩ. This value is high enough to be easily driven by the

LMV793/LMV794, yet small enough to minimize the effects from the parasitic capacitance of both the PCB and

the op amp.

Note: When using the LMV793/LMV794, proper high frequency PCB layout must be followed. The GBW of these

parts is 88 MHz, making the PCB layout significantly more critical than when using the compensated

counterparts which have a GBW of 17 MHz.

TRANSIMPEDANCE AMPLIFIER

An excellent application for either the LMV793 or the LMV794 is as a transimpedance amplifier. With a GBW

product of 88 MHz these parts are ideal for high speed data transmission by light. The circuit shown on the front

page of the datasheet is the circuit used to test the LMV793/LMV794 as transimpedance amplifiers. The only

change is that VB is tied to the VCC of the part, thus the direction of the diode is reversed from the circuit shown

on the front page.

Very high speed components were used in testing to check the limits of the LMV793/LMV794 in a

transimpedance configuration. The photo diode part number is PIN-HR040 from OSI Optoelectronics. The diode

capacitance for this part is only about 7 pF for the 2.5V bias used (VCC to virtual ground). The rise time for this

diode is 1 nsec. A laser diode was used for the light source. Laser diodes have on and off times under 5 nsec.

The speed of the selected optical components allowed an accurate evaluation of the LMV793 as a

transimpedance amplifier. TIs Evaluation Board for decompensated op amps, PN 551013271-001 A, was used

and only minor modifications were necessary and no traces had to be cut.

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