MCP6141 View Datasheet(PDF) - Microchip Technology
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MCP6141 Datasheet PDF : 38 Pages
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MCP6141/2/3/4
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
supply rail with a 50 kΩ 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
maximum 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
glitching 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
excessive battery drain. Driving a DC voltage of 2.5V
across a 100 kΩ load resistor will cause the supply
current to increase by 25 µA, depleting the battery 43
times as fast as IQ (0.6 µA, typical) alone.
High frequency signals (fast edge rate) across
capacitive loads will also significantly increase supply
current. For instance, a 0.1 µF capacitor at the output
presents an AC impedance of 15.9 kΩ (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 4-1:
PSupply = (VDD - VSS) (IQ + VL(p-p) f CL )
= (5V)(0.6 µA + 5.0Vp-p · 100Hz · 0.1µF)
= 3.0 µW + 50 µW
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 4-3 and Figure 4-4 have their noise gain
calculated as follows:
EQUATION 4-2:
GN
=
1 + -R----F- ≥ 10
RG
V/V
In order for the amplifiers to be stable, the noise gain
should meet the specified minimum noise gain. Note
that a noise gain of GN = +10 V/V corresponds to a
non-inverting signal gain of G = +10 V/V, or to an
inverting signal gain of G = -9 V/V.
RIN
VIN
RG
MCP614X
RF
VOUT
FIGURE 4-3:
Noise Gain for Non-inverting
Gain Configuration.
RG
VIN
RIN
RF
MCP614X
VOUT
FIGURE 4-4:
Noise Gain for Inverting
Gain Configuration.
DS21668D-page 16
© 2009 Microchip Technology Inc.
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