MCP632 datasheet(25/42 Pages) MICROCHIP

25 / 42 page

DS22197A-page 25

MCP631/2/3/5

Sometimes, it helps to place guard traces next to victim

traces. They should be on both sides of the victim

trace, and as close as possible. Connect guard traces

to ground plane at both ends, and in the middle for long

traces.

Use coax cables, or low inductance wiring, to route

signal and power to and from the PCB. Mutual and self

inductance of power wires is often a cause of crosstalk

and unusual behavior.

4.7

Typical Applications

4.7.1

POWER DRIVER WITH HIGH GAIN

Figure 4-10 shows a power driver with high gain

(1 + R2/R1). The MCP631/2/3/5 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 4-10:

Power Driver.

4.7.2

OPTICAL DETECTOR AMPLIFIER

Figure 4-11 shows a transimpedance amplifier, using

the MCP63X op amp, in a photo detector circuit. The

photo detector is a capacitive current source.

RF provides enough gain to produce 10 mV at VOUT.

CF stabilizes the gain and limits the transimpedance

bandwidth

about

1.1 MHz.

RF’s parasitic

capacitance (e.g., 0.2 pF for a 0805 SMD) acts in

parallel with CF.

FIGURE 4-11:

Transimpedance Amplifier

for an Optical Detector.

4.7.3

H-BRIDGE DRIVER

Figure 4-12 shows the MCP632 dual op amp used as

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

motor.

FIGURE 4-12:

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 4-7 shows how to calculate RGT and

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

GDM needs to be selected first.

EQUATION 4-7:

Equation 4-8 gives the resulting common mode and

differential mode output voltages.

EQUATION 4-8:

VIN

VDD/2

VOUT

MCP63X

Photo

Detector

VDD/2

30pF

100 k

1.5 pF

100 nA

VOUT

MCP63X

VIN

VOT

RGB

VOB

VDD/2

RGT

½ MCP632

–

DD 2

⁄

–

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

1 V/V

≥

≡

DM 2

⁄

() 1

–

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

DM 2

⁄

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

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

-----------

–

DM VIN

-----------

–

⎝⎠

⎛⎞

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