Datasheet

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 2009-2011 Microchip Technology Inc. DS22146C-page 29

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

4.7 Typical Applications

4.7.1 POWER DRIVER WITH HIGH GAIN

Figure 4-13 shows a power driver with high gain

(1 + R

). 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. R

should be small,

and equal to R

||R

, 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 C

. R

provides enough gain to

produce 10 mV at V

OUT

. C

stabilizes the gain and lim-

its the transimpedance bandwidth to about 1.1 MHz.

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

SMD) acts in parallel with C

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 (G

)

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 R

and

so that both op amps have the same DC gains;

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

/2 V

OUT

Photo

Detector

MCP651

30pF

100 k

1.5 pF

100 nA

OUT

½ MCP652

–



–

-------------------------------- 2 V / V





1–

---------------------------------=



-------------------=

V+

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

-----------=

V–

-----------

–



