CA3140M Intersil, CA3140M Datasheet - Page 16

• Manufacturer Part Number: CA3140M
• Description: IC OP AMP BIMOS 4.5MHZ 8-SOIC
• Manufacturer: Intersil

Specifications of CA3140M

• Amplifier Type: General Purpose
• Number Of Circuits: 1
• Slew Rate: 9 V/µs
• Gain Bandwidth Product: 4.5MHz
• Current - Input Bias: 10pA
• Voltage - Input Offset: 5000µV
• Current - Supply: 4mA
• Current - Output / Channel: 40mA
• Voltage - Supply, Single/dual (±): 4 V ~ 36 V, ±2 V ~ 18 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Output Type: -
• -3db Bandwidth: -

Wien Bridge Oscillator
Another application of the CA3140 that makes excellent use
of its high input impedance, high slew rate, and high voltage
qualities is the Wien Bridge sine wave oscillator. A basic Wien
Bridge oscillator is shown in Figure 21. When R
and C
familiar f = 1/(2πRC) and the gain required for oscillation,
A
four and R
for oscillation becomes 1.5, thus permitting a potentially
higher operating frequency closer to the gain bandwidth
product of the CA3140.
Oscillator stabilization takes on many forms. It must be
precisely set, otherwise the amplitude will either diminish or
reach some form of limiting with high levels of distortion. The
element, R
resistance element. Thus, through some control means, the
value of R
A FET channel resistance, a thermistor, a lamp bulb, or other
device whose resistance increases as the output amplitude
is increased are a few of the elements often utilized.
Figure 22 shows another means of stabilizing the oscillator
with a zener diode shunting the feedback resistor (R
Figure 21). As the output signal amplitude increases, the
zener diode impedance decreases resulting in more
feedback with consequent reduction in gain; thus stabilizing
the amplitude of the output signal. Furthermore, this
combination of a monolithic zener diode and bridge rectifier
circuit tends to provide a zero temperature coefficient for this
regulating system. Because this bridge rectifier system has
no time constant, i.e., thermal time constant for the lamp
bulb, and RC time constant for filters often used in detector
networks, there is no lower frequency limit. For example, with
1µF polycarbonate capacitors and 22MΩ for the frequency
determining network, the operating frequency is 0.007Hz.
As the frequency is increased, the output amplitude must be
reduced to prevent the output signal from becoming slew-
rate limited. An output frequency of 180kHz will reach a slew
rate of approximately 9V/µs when its amplitude is 16V
C
FIGURE 21. BASIC WIEN BRIDGE OSCILLATOR CIRCUIT
OSC
1
1
is equal to 3. Note that if C
= C
C
R
S
2
2
1
S
2
is adjusted to maintain constant oscillator output.
is reduced by a factor of four, the gain required
, is commonly replaced with some variable
USING AN OPERATIONAL AMPLIFIER
= C, the frequency equation reduces to the
+
-
R
2
OUTPUT
R
R
F
S
16
NOTES:
2
is increased by a factor of
A
A
OSC
CL
f
=
=
------------------------------------------ -
2π R
=
1
1
1
+
= R
+
R
------- -
R
1
S
C
C
------ -
C
F
1
1
1
2
2
CA3140, CA3140A
F
R
+
= R
P-P
of
2
R
------ -
R
C
2
1
2
.
Simple Sample-and-Hold System
Figure 23 shows a very simple sample-and-hold system
using the CA3140 as the readout amplifier for the storage
capacitor. The CA3080A serves as both input buffer amplifier
and low feed-through transmission switch (see Note 13).
System offset nulling is accomplished with the CA3140 via
its offset nulling terminals. A typical simulated load of 2kΩ
and 30pF is shown in the schematic.
INPUT
In this circuit, the storage compensation capacitance (C
only 200pF. Larger value capacitors provide longer “hold”
periods but with slower slew rates. The slew rate is:
NOTE:
13. AN6668 “Applications of the CA3080 and CA 3080A High
R
FIGURE 22. WIEN BRIDGE OSCILLATOR CIRCUIT USING
1
C
dv
----- -
dt
R
2
Performance Operational Transconductance Amplifiers”.
1
STROBE
= R
=
R
1000pF
2
--- -
C
C
1000
pF
2
100Hz, R = 1.6MΩ
10kHz, R = 16MΩ
30kHz, R = 5.1MΩ
I
2kΩ
1
50Hz, R = 3.3MΩ
1kHz, R = 160MΩ
= R
FIGURE 23. SAMPLE AND HOLD CIRCUIT
=
CA3140
0.5mA 200pF
3
2
200pF
1N914
1N914
30kΩ
2kΩ
3
2
CA3140
+
-
0.1µF
+15V
-15V
⁄
7
4
+
CA3080A
-
5
SUBSTRATE
0.1µF
+15V
-15V
200pF
OF CA3019
400Ω
0.1µF
7
4
6
=
0.1µF
-15
7.5kΩ
3.6kΩ
500Ω
0
2.5V µs
7
6
C
1
⁄
SIMULATED LOAD
CA3109
NOT REQUIRED
ARRAY
3
2
DIODE
6
SAMPLE
HOLD
100kΩ
OUTPUT
19V
THD <0.3%
CA3140
+
-
5
0.1µF
P-P
2kΩ
+15V
7
1
TO 22V
0.1µF
8
5
4
-15V
30pF
P-P
0.1
µF
6
July 11, 2005
FN957.10
2
3.5kΩ
1
) is
9
1
3
4
2kΩ