MCP6V06 Microchip Technology Inc., MCP6V06 Datasheet - Page 22

• Manufacturer Part Number: MCP6V06
• Description: 300 ?a, Auto-zeroed Op Amps
• Manufacturer: Microchip Technology Inc.

MCP6V06/7/8
4.1.2
Figure 4-2
during the Normal Mode of operation (φ
capacitor (C
Since the Null Amplifier has very high gain, it
dominates the signal seen by the Main Amplifier. This
greatly reduces the impact of the Main Amplifier’s input
FIGURE 4-2:
Figure 4-3
during the Auto-zeroing Mode of operation (φ
signal goes directly through the Main Amplifier, and the
flywheel capacitor (C
tion on the Main Amplifier’s offset.
The Null Amplifier uses its own high open loop gain to
drive the voltage across C
offset voltage is almost zero. Because the principal
input is connected to V
corrects the offset at the current common mode input
voltage (V
the DC CMRR and PSRR very high also.
FIGURE 4-3:
4.1.3
The MCP6V06/7/8 op amps will show intermodulation
distortion (IMD), products when an AC signal is
present.
The signal and clock can be decomposed into sine
wave tones (Fourier series components). These tones
interact with the auto-zeroing circuitry’s non-linear
response to produce IMD tones at sum and difference
DS22093B-page 22
V
V
V
V
IN
IN
IN
IN
CM
+
–
+
–
shows the connections between amplifiers
shows the connections between amplifiers
AUTO-ZEROING ACTION
INTERMODULATION DISTORTION
(IMD)
H
) and supply voltage (V
) corrects the Null Amplifier’s input offset.
C
C
H
H
FW
Normal Mode of Operation (
Auto-zeroing Mode of Operation (
) maintains a constant correc-
IN
H
+, the auto-zeroing action
to the point where its input
Amp.
Amp.
Null
Null
DD
). This makes
1
). The hold
2
C
C
). The
FW
FW
φ
1
); Equivalent Amplifier Diagram.
φ
2
); Equivalent Diagram.
Amp.
Amp.
Main
Main
offset voltage on overall performance. Essentially, the
Null Amplifier and Main Amplifier behave as a regular
op amp with very high gain (A
voltage (V
Since these corrections happen every 50 µs, or so, we
also minimize slow errors, including offset drift with
temperature (ΔV
aging.
frequencies. IMD distortion tones are generated about
all of the square wave clock’s harmonics. See
Figure 2-37
OS
and
).
V
V
NC
NC
REF
REF
Figure
OS
/ΔT
A
2-38.
© 2008 Microchip Technology Inc.
), 1/f noise, and input offset
Output
Output
Buffer
Buffer
OL
) and very low offset
V
V
OUT
OUT