MCP6141 datasheet(12/34 Pages) MICROCHIP

12 / 34 page

MCP6141/2/3/4

DS21668B-page 12

4.0

APPLICATIONS INFORMATION

The MCP6141/2/3/4 family of op amps is manufactured

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

These op amps are stable for gains of 10 V/V and

higher. They are suitable for a wide range of general

purpose, low-power applications.

See Microchip’s related MCP6041/2/3/4 family of op

amps for applications needing unity gain stability.

4.1

Rail-to-Rail Inputs

The MCP6141/2/3/4 op amps are designed to prevent

phase reversal when the input pins exceed the supply

voltages. Figure 2-10 shows the input voltage exceed-

ing the supply voltage without any phase reversal.

The input stage of the MCP6141/2/3/4 op amps uses

two differential CMOS input stages in parallel. One

operates at low Common mode input voltage (VCM),

while the other operates at high VCM. With this topol-

ogy, the device operates with VCM tp to 0.3V above VDD

and 0.3V below VSS. The input offset voltage (VOS) is

measured at VCM =VSS – 0.3V and VDD + 0.3V to

ensure proper operation.

Input voltages that exceed the Absolute Maximum Volt-

age Range (VSS – 0.3V to VDD + 0.3V) can cause

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

Current beyond ±2 mA can cause reliability problems.

Applications that exceed this rating must be externally

limited with a resistor, as shown in Figure 4-1.

FIGURE 4-1:

Input Current-Limiting

Resistor (RIN).

4.2

Rail-to-Rail Output

There are two specifications that describe the output

swing capability of the MCP6141/2/3/4 family of op

amps. The first specification (Maximum Output Voltage

Swing) defines the absolute maximum swing that can

be achieved under the specified load condition. Thus,

the output voltage swings to within 10 mV of either sup-

ply rail with a 50 k

Ω load to VDD/2. Figure 2-10 shows

how the output voltage is limited when the input goes

beyond the linear region of operation.

The second specification that describes the output

swing capability of these amplifiers is the Linear Output

Voltage Range. This specification defines the maxi-

mum output swing that can be achieved while the

amplifier still operates in its linear region. To verify

linear operation in this range, the large signal DC

Open-Loop Gain (AOL) is measured at points inside the

supply rails. The measurement must meet the specified

AOL condition in the specification table.

4.3

Output Loads and Battery Life

The MCP6141/2/3/4 op amp family has outstanding

quiescent current, which supports battery-powered

applications. There is minimal quiescent current glitch-

ing when Chip Select (CS) is raised or lowered. This

prevents excessive 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 sin-

ewave. 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 4-1:

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

4.4

Stability

4.4.1

NOISE GAIN

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

high bandwidth and slew rate for circuits with high noise

gain (GN) or signal gain. Low gain applications should

be realized using the MCP6041/2/3/4 op amp family;

this simplifies design and implementation issues.

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. The amplifier circuits

in Figure 4-2 and Figure 4-3 have their noise gain

calculated as follows:

Maximum expected V

() V

–

2 mA

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

≥

Minimum expected V

()

–

2 mA

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

≥

MCP614X

RIN

VOUT

RIN

PSupply = (VDD - VSS) (IQ + VL(p-p) f CL )

= (5V)(0.6 µA + 5.0Vp-p · 100Hz · 0.1µF)

= 3.0 µW + 50 µW

MCP6141 датащи(PDF) 12 Page - Microchip Technology

MCP6141 датащи(HTML) 12 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

датащи скачать

ссылки URL