 2003 Microchip Technology Inc.

DS21733D-page 7

MCP6001/2/4

3.0

APPLICATION INFORMATION

The MCP6001/2/4 family of op amps is manufactured

using Microchip’s state-of-the-art CMOS process and

is specifically designed for low cost, low power and

general-purpose applications. The low supply voltage,

low quiescent current and wide bandwidth makes the

MCP6001/2/4 ideal for battery-powered applications.

This device has high phase margin, which makes it

stable for larger capacitive load applications.

3.1

Rail-to-Rail Input

The MCP6001/2/4 op amp is designed to prevent

phase reversal when the input pins exceed the supply

voltages. Figure 3-1 shows the input voltage exceeding

the supply voltage without any phase reversal.

FIGURE 3-1:

The MCP6001/2/4 Shows

No Phase Reversal.

The input stage of the MCP6001/2/4 op amp uses two

differential input stages in parallel; one operates at low

The

Input

Offset

Voltage

is

measured

at

proper operation.

Input voltages that exceed the input voltage range

sive current to flow into or out of the input pins. Current

beyond ±2 mA can cause reliability problems. Applica-

tions that exceed this rating must be externally limited

with a resistor, as shown in Figure 3-2.

FIGURE 3-2:

Input Current Limiting

3.2

Rail-to-Rail Output

The output voltage range of the MCP6001/2/4 op amp

Refer to Figure 2-14 for more information.

3.3

Capacitive Loads

Driving large capacitive loads can cause stability prob-

lems for voltage feedback op amps. As the load capac-

itance increases, the feedback loop’s phase margin

decreases, and the closed loop bandwidth is reduced.

This produces gain peaking in the frequency response,

with overshoot and ringing in the step response. A unity

gain buffer (G = +1) is the most sensitive to capacitive

loads, but all gains show the same general behavior.

When driving large capacitive loads with these op

amps (e.g., > 100 pF when G = +1), a small series

feedback loop’s phase margin (stability) by making the

output load resistive at higher frequencies. It does not,

however, improve the bandwidth.

FIGURE 3-3:

stabilizes large capacitive loads.

(or step response overshoot) on the bench (or with the

MCP6001/2/4 Spice macro model). If the response is

reasonable.

-1

0

1

2

3

4

5

6

0.E+00

1.E-05

2.E-05

3.E-05

4.E-05

5.E-05

6.E-05

7.E-05

8.E-05

9.E-05

1.E-04

Time (10 µs/div)

G = +2 V/V

()

–

2 mA

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

≥

–

2 mA

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

≥

MCP600X

–

+

MCP600X

–

+