CA3140AS INTERSIL [Intersil Corporation], CA3140AS Datasheet - Page 19

• Manufacturer Part Number: CA3140AS
• Description: 4.5MHz, BiMOS Operational Amplifier with MOSFET Input/Bipolar Output
• Manufacturer: INTERSIL [Intersil Corporation]

represents the typical leakage current of the CA3080A when
strobed off. If C
rate will decrease to 0.085 V/ s, but the slew rate would
decrease to 0.25V/ s. The parallel diode network connected
between terminal 3 of the CA3080A and terminal 6 of the
CA3140 prevents large input signal feedthrough across the
input terminals of the CA3080A to the 200pF storage capacitor
when the CA3080A is strobed off. Figure 32 shows dynamic
characteristic waveforms of this sample-and-hold system.
FIGURE 32. SAMPLE AND HOLD SYSTEM DYNAMIC CHARAC-
Center Trace: Difference of Input and Output Signals through
Bottom Trace: Input Signal; 5V/Div and 2 s/Div
Top Trace: Output Signal; 5V/Div and 2 s/Div
LARGE SIGNAL RESPONSE AND SETTLING TIME
Bottom Trace: Input; 50mV/Div and 200ns/Div
Bottom Trace: Input; 20V/Div and 500ns/Div
Top Trace: Output; 50mV/Div and 200ns/Div
Top Trace: Output; 100mV/Div and 500ns/Div
TERISTICS WAVEFORMS
Tektronix Amplifier 7A13; 5mV/Div and 2 s/Div
1
were increased to 2000 pF, the “hold-droop”
SAMPLING RESPONSE
CA3140, CA3140A
2-141
Current Amplifier
The low input terminal current needed to drive the CA3140
makes it ideal for use in current amplifier applications such
as the one shown in Figure 33.* In this circuit, low current is
supplied at the input potential as the power supply to load
resistor R
tion factor R2/R1, when the load current is monitored by the
power supply meter M. Thus, if the load current is 100nA,
with values shown, the load current presented to the supply
will be 100 A; a much easier current to measure in many
systems.
Note that the input and output voltages are transferred at the
same potential and only the output current is multiplied by
the scale factor.
The dotted components show a method of decoupling the
circuit from the effects of high output load capacitance and
the potential oscillation in this situation. Essentially, the
necessary high frequency feedback is provided by the
capacitor with the dotted series resistor providing load
decoupling.
Figure 34 shows a single supply, absolute value, ideal full-
wave rectifier with associated waveforms. During positive
excursions, the input signal is fed through the feedback
network directly to the output. Simultaneously, the positive
excursion of the input signal also drives the output terminal
(No. 6) of the inverting amplifier in a negative going
excursion such that the 1N914 diode effectively disconnects
the amplifier from the signal path. During a negative going
excursion of the input signal, the CA3140 functions as a
normal inverting amplifier with a gain equal to -R2/R1. When
the equality of the two equations shown in Figure 34 is
satisfied, the full wave output is symmetrical.
* “Operational Amplifiers Design and Applications”, J. G. Graeme,
FIGURE 33. BASIC CURRENT AMPLIFIER FOR LOW CURRENT
McGraw-Hill Book Company, page 308 - “Negative Immittance
Converter Circuits”.
SUPPLY
POWER
M
I
L
L
R2
R1
. This load current is increased by the multiplica-
MEASUREMENT SYSTEMS
3
2
100k
10k
R1
+
CA3140
-
5
4.3k
1
+15V
-15V
7
4
0.1 F
6
0.1 F
10M
R2
I
R
L
L