MCP6001RT-E/LO Ver la hoja de datos (PDF) - Microchip Technology

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MCP6001RT-E/LO

1 MHz Bandwidth Low Power Op Amp

Microchip Technology 

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.

6

VIN

5

VOUT

4

VDD = 5.0V

G = +2 V/V

3

2

1

0

-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)

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

common mode input voltage (VCM) and the other at

high VCM. With this topology, the device operates with

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 exces-

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.

MCP6001/2/4

–

RIN

MCP600X

VIN

+

VOUT

RIN

≥

(---M-----a---x---i-m----u---m------e---x---p---e--c---t--e--d-----V----I--N----)---–-----V---D----D--

2 mA

RIN

≥

-V---S---S----–----(---M-----i--n---i-m-----u---m-----e---x---p---e--c---t--e--d-----V----I--N----)

2 mA

FIGURE 3-2:

Resistor (RIN).

Input Current Limiting

3.2 Rail-to-Rail Output

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

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

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

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

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

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

output load resistive at higher frequencies. It does not,

however, improve the bandwidth.

–

RISO

MCP600X

VIN

+

CL

VOUT

FIGURE 3-3:

Output resistor, RISO

stabilizes large capacitive loads.

To select RISO, check the frequency response peaking

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

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

reasonable, you do not need RISO. Otherwise, start

RISO at 1 kΩ and modify its value until the response is

reasonable.

 2003 Microchip Technology Inc.

DS21733D-page 7

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