MCP4011-103ESLASHMS datasheet(45/60 Pages) MICROCHIP

45 / 60 page

DS21978C-page 45

MCP4011/2/3/4

8.2

Operational Amplifier

Applications

Figure 8-3, Figure 8-4 and Figure 8-5 illustrate typical

amplifier circuits that could replace fixed resistors with

the MCP4011/2/3/4 to achieve digitally-adjustable

analog solutions.

Figure 8-4 shows a circuit that allows a non-inverting

amplifier to have its’ offset and gain to be independently

trimmed. The MCP4011 is used along with resistors R1

and R2 to set the offset voltage. The sum of R1 + R2

resistance should be significantly greater (> 100 times)

the resistance value of the MCP4011. This allows each

increment or decrement in the MCP4011 to be a fine

adjustment of the offset voltage. The input voltage of

the op amp (V

IN) should be centered at the op amps V

voltage. The gain is adjusted by the MCP4012. If the

resistance value of the MCP4012 is small compared to

the resistance value of R3, then this is a fine adjustment

of the gain. If the resistance value of the MCP4012 is

equal (or large) compared to the resistance value of R3,

then this is a course adjustment of the gain. In general,

trim the course adjustments first and then trim the fine

adjustments.

FIGURE 8-3:

Trimming Offset and Gain in

an Inverting Amplifier.

FIGURE 8-4:

Trimming Offset and Gain in

a Non-Inverting Amplifier.

FIGURE 8-5:

Programmable Filter.

Op Amp

VIN

VOUT

–

MCP4011

VDD

MCP6001

Op Amp

VIN

VOUT

–

VDD

MCP6291

MCP4012

Op Amp

VIN

VOUT

–

MCP4011

VDD

MCP4011

π R

Eq C

⋅⋅

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

Pot1

Pot2

REq

R1 RAB RWB

–

()

R2 RWB

() R

Thevenin

Equivalent

MCP6021

MCP4011-103E/MS Datasheet(PDF) 45 Page - Microchip Technology

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