CMV1016 Datasheet, PDF (11/12 Pages) California Micro Devices Corp – MICROPOWER PRO OPERATIONAL AMPLIFIER WITH SHUTDOWN

CALIFORNIA MICRO DEVICES
CMV1016
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1
——————— ≥ ——————
2 ∏ R_S C_S
2 ∏ R_F C_F
Since the parasitic capacitance can change between
the breadboard and the production printed circuit
board, we favor the use of a "gimmick", a technique
perfected by TV technicians in the 1950’s. A gimmick
is made by taking two lengths (typically about a foot)
of small gauge wire such as AWG 24, twisting them
together, and then after baring all ends soldering the
gimmick across R_F. With the circuit operating, C_F is
"adjusted" by clipping short lengths of the gimmick off
until the compensation is nominal. Then simply
remove the gimmick, take it to an impedance bridge,
and select the capacitor accordingly.
Figure 2.
4. Capacitive Load Considerations
The CMV1016 is capable of driving capacitate loads in
excess of 100pF without oscillation. However, signifi-
cant peaking will result. Probably the easiest way
minimize this problem is to use an isolation resistor as
shown in Figure 3.
5. Power Supply Decoupling
The CMV1016 is not prone to oscillation without the
use of power supply decoupling capacitors, however to
minimize hum and noise pick-up, it is recommended
that the rails be bypassed with 0.01µF capacitors.
6. Turn On and Turn Off (Shut Down)
Characteristics
The turn off delay (Disable Response), t_OFF, is defined
as the time between the shut down signal crossing the
disable threshold (typically V+ – 1 volt) and the time
for the amplifier’s output to come within 10% of zero. It
is largely governed by a propagation delay within the
CMV1016 of few hundred nanoseconds followed by an
exponential decay determined by the load resistance
in parallel with the load capacitance.
The turn on delay (Enable Response), t_ON, is defined
as the time between the shutdown signal crossing the
threshold and the time the output reaches to within
10% of its final value. t_ON is largely independent of
supply voltage and input level.
7. Typical Applications
Illustrated in Figure 4 is a Sample and Hold Amplifier
capable of operating from a single rail, but it will work
equally well with split rails The circuit will accommo-
date input voltages (common mode) from zero volts to
V+ – 1 volt. The Shut Down feature of the CMV1016 is
used to disable A₁ whose output acts like a very high
impedance in this mode. The high slew rate of the
CMV1016 and large output current minimize
Acquisition Time. A₂ presents a very high input
impedance and very low bias current. A Logic "1", a
voltage > V+ – 1 volt will put the circuit into "Sample"
mode. A Logic “0” will put the circuit in "Hold" mode.
For the values shown, Acquisition Time to 0.1% is
typically 10µs for a zero to 4 volt input, the hold step
is typically 400µV, and the droop rate at 85°C is
0.1µV/µs. Overall accuracy is better than 0.01%. For
minimum droop, C₁ should be of polystyrene
construction.
Figure 3
Figure 4
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