MCP6482 datasheet(19/50 Pages) MICROCHIP

部品番号	MCP6482

部品情報	4 MHz, Low-Input Bias Current Op Amps

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メーカー	MICROCHIP [Microchip Technology]

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 2012-2013 Microchip Technology Inc.

DS20002322C-page 19

MCP6481/2/4

4.7.3

PH ELECTRODE AMPLIFIER

The MCP6481/2/4 op amps can be used for sensing

applications where the sensor has high output

impedance, such as a pH electrode sensor; its output

impedance is in the range of 1 M

 to 1G. The key op

amp specifications for these kinds of applications are

low-input bias current and high input impedance.

A typical sensing circuit is shown in Figure 4-12, it is

implemented with a non-inverting amplifier which has a

gain of 1+R2/R1. The input voltage error due to input

bias current is equal to IB*ROUT, which is amplified by

1+R2/R1 at the output. To minimize the voltage error

and get the VOUT with better accuracy, the IB must be

small enough.

FIGURE 4-12:

pH Electrode Amplifier.

VOUT

VIN

–

pH electrode

VSEN

VSEN is the sensed voltage by pH electrode

ROUT is the pH electrode’s output impedance

–

ROUT

MCP648X

MCP6482 データシート(PDF) 19 Page - Microchip Technology