MCP652 datasheet(28/62 Pages) MICROCHIP

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MCP651/1S/2/3/4/5/9

DS20002146D-page 28

 2009-2014 Microchip Technology Inc.

4.7

Typical Applications

4.7.1

POWER DRIVER WITH HIGH GAIN

Figure 4-13 shows a power driver with high gain

(1 + R2/R1). The MCP651/1S/2/3/4/5/9 op amp’s short-

circuit current makes it possible to drive significant

loads. The calibrated input offset voltage supports

accurate response at high gains. R3 should be small,

and equal to R1||R2, in order to minimize the bias

current induced offset.

FIGURE 4-13:

Power Driver.

4.7.2

OPTICAL DETECTOR AMPLIFIER

Figure 4-14 shows a transimpedance amplifier, using

the MCP651 op amp, in a photo detector circuit. The

photo detector is a capacitive current source. The op

amp’s input Common mode capacitance (5 pF, typical)

acts in parallel with CD. RF provides enough gain to

produce 10 mV at VOUT. CF stabilizes the gain and lim-

its the transimpedance bandwidth to about 1.1 MHz.

RF’s parasitic capacitance (e.g., 0.2 pF for a 0805

SMD) acts in parallel with CF.

FIGURE 4-14:

Transimpedance Amplifier

for an Optical Detector.

4.7.3

H-BRIDGE DRIVER

Figure 4-15 shows the MCP652 dual op amp used as

a H-bridge driver. The load could be a speaker or a DC

motor.

FIGURE 4-15:

H-Bridge Driver.

This circuit automatically makes the noise gains (GN)

equal, when the gains are set properly, so that the

frequency responses match well (in magnitude and in

phase). Equation 4-11 shows how to calculate RGT and

RGB so that both op amps have the same DC gains;

GDM needs to be selected first.

EQUATION 4-11:

Equation 4-12 gives the resulting Common mode and

Differential mode output voltages.

EQUATION 4-12:

MCP65X

VIN

VDD/2

VOUT

Photo

Detector

VDD/2

MCP651

30 pF

100 k



1.5 pF

100 nA

VOUT

½ MCP652

VIN

VOT

½ MCP652

RGB

VOB

VDD/2

RGT

–

DD 2



–

--------------------------------

2 V/V





DM 2



 1

–

---------------------------------

DM 2



-------------------

---------------------------

-----------

–

DM VIN

-----------

–





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