MCP6141 datasheet(10/32 Pages) MICROCHIP

10 / 32 page

MCP6141/2/3/4

21668A-page 10

2002 Microchip Technology Inc.

3.0

APPLICATIONS INFORMATION

The MCP6141/2/3/4 family of operational amplifiers

are fabricated on Microchip’s state-of-the-art CMOS

process. They are stable for noise gain of 10 V/V or

higher. Microchip also produces a unity gain stable

product, the MCP6041/2/3/4 family, which has similar

specifications. The MCP6041/2/3/4 family has a band-

width of 1.4 kHz at a noise gain of 10 V/V, while the

MCP6141/2/3/4 family has a bandwidth of 10 kHz at a

noise gain of 10 V/V. These devices are suitable for a

wide range of applications requiring very low power

consumption. With these op amps, the power supply

pin needs to be bypassed with a 0.1 µF capacitor.

3.1

Rail-to-Rail Input

The input stage of these devices uses two differential

input stages in parallel; one operates at low VCM (com-

mon mode input voltage) and the other at high VCM.

With this topology, the MCP6141/2/3/4 family operates

with VCM up to 300 mV past either supply rail. The Input

Offset Voltage is measured at both VCM =VSS -0.3V

and VDD + 0.3V to ensure proper operation.

3.2

Output Loads and Battery Life

The MCP6141/2/3/4 op amp family has low quiescent

current, which supports battery-powered applications.

There is minimal quiescent current glitch when chip

select (CS) is raised or lowered. This prevents exces-

sive current draw and reduced battery life when the

part is turned off or on.

Heavy resistive loads at the output can cause exces-

sive battery drain. Driving a DC voltage of 2.5V across

a 100 k

Ω load resistor will cause the supply current to

increase by 25 µA, depleting the battery 43 times as

fast as IQ (0.6 µA typ) alone.

High frequency signals (fast edge rate) across capaci-

tive loads will also significantly increase supply current.

For instance, a 0.1 µF capacitor at the output presents

an AC impedance of 15.9 k

Ω (1/2πfC) to a 100 Hz

sinewave. It can be shown that the average power

drawn from the battery by a 5.0 Vp-p sinewave

(1.77 Vrms) under these conditions is:

EQUATION

This will drain the battery 18 times as fast as IQ alone.

3.3

Rail-to-Rail Output

The MCP6141/2/3/4 family Maximum Output Voltage

Swing defines the maximum swing possible under a

particular output load. According to the specification

table, the output can reach up to 10 mV of either supply

rail with a 50 k

Ω load.

3.4

Input Voltage and Phase Reversal

The MCP6141/2/3/4 op amp family uses CMOS tran-

sistors at the input. It is designed to prevent phase

reversal when the input pins exceed the supply volt-

ages. Figure 2-33 shows an input voltage exceeding

both supplies without output phase reversal.

The maximum operating VCM that can be applied to the

inputs is VSS -0.3V and VDD + 0.3V. Voltage on the

input that exceeds this absolute maximum rating can

cause excessive current to flow in or out of the input

pins. Current beyond ±2 mA can cause possible reli-

ability problems. Applications that exceed this rating

must be externally limited with an input resistor, as

shown in Figure 3-1.

FIGURE 3-1:

An input resistor, RIN,

should be used to limit excessive input current if

the inputs exceed the absolute maximum

specification.

3.5

Stability

The MCP6141/2/3/4 op amp family is designed to give

high bandwidth and faster slew rate for circuits with

high noise (Gn) or signal gain. The related unity-gain

stable MCP6041/2/3/4 op amp family has lower AC

performance, but it is preferable for low noise gain

applications.

Noise gain is defined to be the gain from a voltage

source at the non-inverting input to the output when all

other voltage sources are zeroed (shorted out). Noise

gain is independent of signal gain and depends only on

components in the feedback loop.

PSUPPLY

VDD VSS

–

() IQ VLp p

–

()

fCL

()

3.0

µW50µW

() 0.6µA5.0V

–

100Hz 0.1

µF

⋅⋅

()

RIN

VSS

Minimum expected VIN

()

–

2 mA

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

≥

RIN

Maximum expected VIN

() VDD

–

2 mA

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

≥

VIN

RIN

VOUT

MCP614X

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