MCP6001 datasheet(8/28 Pages) MICROCHIP

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MCP6001/2/4

DS21733F-page 8

4.0

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.

4.1

Rail-to-Rail Input

The MCP6001/2/4 op amps are designed to prevent

phase reversal when the input pins exceed the supply

voltages. Figure 4-1 shows the input voltage exceeding

the supply voltage without any phase reversal.

FIGURE 4-1:

The MCP6001/2/4 Show No

Phase Reversal.

The input stage of the MCP6001/2/4 op amps use two

differential input stages in parallel. One operates at a

low common mode input voltage (VCM), while the other

operates at a high VCM. With this topology, the device

operates with a VCM up to 300 mV above VDD and

300 mV below VSS. The input offset voltage is

measured at VCM =VSS – 300 mV and VDD +300 mV

to ensure proper operation.

Input voltages that exceed the input voltage range

(VSS – 0.3V to VDD + 0.3V at 25°C) can cause

excessive current to flow into or out of the input pins,

while current beyond ±2 mA can cause reliability

problems. Applications that exceed this rating must be

externally limited with a resistor, as shown in Figure 4-2.

FIGURE 4-2:

Input Current Limiting

Resistor (RIN).

4.2

Rail-to-Rail Output

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

is VDD –25mV (min.) and VSS + 25 mV (max.) when

RL =10kΩ is connected to VDD/2 and VDD = 5.5V.

Refer to Figure 2-14 for more information.

4.3

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. While

a unity-gain buffer (G = +1) is the most sensitive to

capacitive loads, 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

resistor at the output (RISO in Figure 4-3) improves the

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

output load resistive at higher frequencies. The band-

width will be generally lower than the bandwidth with no

capacitance load.

FIGURE 4-3:

Output resistor, RISO

stabilizes large capacitive loads.

-1

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)

VDD = 5.0V

G = +2 V/V

VIN

VOUT

Minimum expected V

()

–

2 mA

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

≥

Maximum expected V

() V

–

2 mA

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

≥

VIN

RIN

VOUT

MCP600X

–

VIN

RISO

VOUT

MCP600X

–

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