12
Error-Amplifier in Regulated-Power Supplies
The CA3130 is an ideal choice for error-amplifier service in
regulated power supplies since it can function as an error-
amplifier when the regulated output voltage is required to
approach zero. Figure 13 shows the schematic diagram of a
40mA power supply capable of providing regulated output
voltage by continuous adjustment over the range from 0V to
13V. Q
3
and Q
4
in lC
2
(a CA3086 transistor-array lC)
function as zeners to provide supply-voltage for the CA3130
comparator (IC
1
). Q
1
,Q
2
, and Q
5
in IC
2
are configured as a
low impedance, temperature-compensated source of
adjustable reference voltage for the error amplifier.
Transistors Q
1
, Q
2
, Q
3
, and Q
4
in lC
3
(another CA3086
transistor-array lC) are connected in parallel as the series-
pass element. Transistor Q
5
in lC
3
functions as a current-
limiting device by diverting base drive from the series-pass
transistors, in accordance with the adjustment of resistor R
2
.
Figure 14 contains the schematic diagram of a regulated
power-supply capable of providing regulated output voltage
by continuous adjustment over the range from 0.1V to 50V
and currents up to 1A. The error amplifier (lC
1
) and circuitry
associated with lC
2
function as previously described,
although the output of lC
1
is boosted by a discrete transistor
(Q
4
) to provide adequate base drive for the Darlington-
connected series-pass transistors Q
1
, Q
2
. Transistor Q
3
functions in the previously described current-limiting circuit.
Multivibrators
The exceptionally high input resistance presented by the
CA3130 is an attractive feature for multivibrator circuit
design because it permits the use of timing circuits with high
R/C ratios. The circuit diagram of a pulse generator (astable
multivibrator), with provisions for independent control of the
“on” and “off” periods, is shown in Figure 15. Resistors R
1
and R
2
are used to bias the CA3130 to the mid-point of the
supply-voltage and R
3
is the feedback resistor. The pulse
repetition rate is selected by positioning S
1
to the desired
position and the rate remains essentially constant when the
resistors which determine “on-period” and “off-period” are
adjusted.
Function Generator
Figure 16 contains a schematic diagram of a function
generator using the CA3130 in the integrator and threshold
detector functions. This circuit generates a triangular or
square-wave output that can be swept over a 1,000,000:1
range (0.1Hz to 100kHz) by means of a single control, R
1
. A
voltage-control input is also available for remote sweep-
control.
FIGURE 14. VOLTAGE REGULATOR CIRCUIT (0.1V TO 50V AT 1A)
6
2
3
1
8
7
4
4.3kΩ
1Ω
+
-
43kΩ
100µF
ERROR
AMPLIFIER
IC
1
VOLTAGE
ADJUST
14
13
100µF
+55V
INPUT
2.2kΩ
+
-
IC
2
CA3086 10, 11
Q
4
Q
1
Q
2
6
REGULATION (NO LOAD TO FULL LOAD): <0.005%
INPUT REGULATION: 0.01%/V
HUM AND NOISE OUTPUT: <250µV
RMS
UP TO 100kHz
+
-
+
-
CA3130
+
-
+
-
1W
3.3kΩ
1W
5µF
9
8, 7
Q
3
1, 2
3
5
4
1kΩ
62kΩ
Q
5
12
10kΩ
Q
2
Q
1
50kΩ
Q
3
1kΩ
2N3055
2N2102
CURRENT
LIMIT
ADJUST
2N5294
2N2102
Q
4
1000pF
10kΩ
8.2kΩ
OUTPUT:
0.1 TO 50V
AT 1A
CA3130, CA3130A
