MCP6242 Ver la hoja de datos (PDF) - Microchip Technology

Número de pieza

componentes Descripción

Fabricante

MCP6242

50 µA, 550 kHz Rail-to-Rail Op Amp

Microchip Technology 

MCP6241/1R/1U/2/4

4.7.2

COMPENSATING FOR THE

PARASITIC CAPACITANCE

In analog circuit design, the PCB parasitic capacitance

can compromise the circuit behavior; Figure 4-9 shows

a typical scenario. If the input of an amplifier sees

parasitic capacitance of several picofarad (CPARA,

which includes the common mode capacitance of 6 pF,

typical) and large RF and RG , the frequency response

of the circuit will include a zero. This parasitic zero

introduces gain peaking and can cause circuit

instability.

VAC

RG

VDC

+

MCP624X

–

RF

VOUT

CPARA

CF

CF

=

CPARA

•

R----G--

RF

FIGURE 4-9:

Effect of Parasitic

Capacitance at the Input.

One solution is to use smaller resistor values to push

the zero to a higher frequency. Another solution is to

compensate by introducing a pole at the point at which

the zero occurs. This can be done by adding CF in

parallel with the feedback resistor (RF). CF needs to be

selected so that the ratio CPARA:CF is equal to the ratio

of RF:RG.

DS21882D-page 14

© 2008 Microchip Technology Inc.

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