MCP632 datasheet(24/60 Pages) MICROCHIP

24 / 60 page

MCP631/2/3/4/5/9

DS20002197C-page 24

 2009-2014 Microchip Technology Inc.

4.6

High-Speed PCB Layout

These op amps are fast enough that a little extra care

in the printed circuit board (PCB) layout can make a

significant difference in performance. Good PCB layout

techniques will help achieve the performance shown in

the specifications and typical performance curves; it

will also help minimize electromagnetic compatibility

(EMC) issues.

Use a solid ground plane. Connect the bypass local

capacitor(s) to this plane with minimal length traces.

This cuts down inductive and capacitive crosstalk.

Separate digital from analog, low-speed from

high-speed, and low-power from high-power. This will

reduce interference.

Keep sensitive traces short and straight. Separate

them from interfering components and traces. This is

especially important for high-frequency (low rise time)

signals.

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 short-circuit current of the

MCP631/2/3/4/5/9 op amps 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 to about 1.1 MHz. The parasitic capacitance

of RF (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.

VIN

VDD/2

VOUT

MCP63X

Photo

Detector

VDD/2

30 pF

100 k



1.5 pF

100 nA

VOUT

MCP632

VIN

VOT

RGB

VOB

VDD/2

RGT

½ MCP633

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