MCP6441 datasheet(16/30 Pages) MICROCHIP

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MCP6441

DS22257A-page 16

4.6.2

PRECISION HALF-WAVE

RECTIFIER

The precision half-wave rectifier, which is also known

as a super diode, is a configuration obtained with an

operational amplifier in order to have a circuit behaving

like an ideal diode and rectifier. It effectively cancels the

forward voltage drop of the diode in such way that very

low level signals can still be rectified, with minimal

error. This can be useful for high-precision signal

processing. The MCP6441 op amp has high input

impedance, low input bias current and rail-to-rail

input/output, which makes this device suitable for

precision rectifier applications.

Figure 4-8 shows a precision half-wave rectifier and its

transfer characteristic. The rectifier’s input impedance

is determined by the input resistor R1. To avoid the

loading effect, it must be driven from a low-impedance

source.

When VIN is greater than zero, D1 is OFF, D2 is ON, and

VOUT is zero. When VIN is less than zero, D1 is ON, D2

is OFF, and VOUT is the VIN with an amplification of

-R2/R1.

The rectifier circuit shown in Figure 4-8 has the benefit

that the op amp never goes in saturation, so the only

thing

affecting

its

frequency

response

the

amplification and the gain bandwidth product.

FIGURE 4-8:

Precision Half-Wave

Rectifier.

4.6.3

INSTRUMENTATION AMPLIFIER

The MCP6441 op amp is well suited for conditioning

sensor

signals

battery-powered

applications.

Figure 4-9 shows a two op amp instrumentation

amplifier, using the MCP6441 device, that works well

for applications requiring rejection of Common Mode

noise at higher gains. The reference voltage (VREF) is

supplied by a low-impedance source. In single supply

applications, VREF is typically VDD/2.

FIGURE 4-9:

Two Op Amp

Instrumentation Amplifier.

VOUT

VIN

VOUT

VIN

-R2/R1

Transfer Characteristic

Precision Half-Wave Rectifier

MCP6441

OUT

–

() 1

------

---------

⎝⎠

⎛⎞

REF

VREF R1

VOUT

MCP6441

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