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The heart of the frequency-determining system is an
operational-transconductance-amplifier (OTA) (see Note 10),
lC
1
, operated as a voltage-controlled current-source. The
output, I
O
, is a current applied directly to the integrating
capacitor, C
1
, in the feedback loop of the integrator lC
2
, using
a CA3130, to provide the triangular-wave output.
Potentiometer R
2
is used to adjust the circuit for slope
symmetry of positive-going and negative-going signal
excursions.
Another CA3130, IC
3
, is used as a controlled switch to set
the excursion limits of the triangular output from the
integrator circuit. Capacitor C
2
is a “peaking adjustment” to
optimize the high-frequency square-wave performance of
the circuit.
Potentiometer R
3
is adjustable to perfect the “amplitude
symmetry” of the square-wave output signals. Output from
the threshold detector is fed back via resistor R
4
to the input
of lC
1
so as to toggle the current source from plus to minus
in generating the linear triangular wave.
Operation with Output-Stage Power-Booster
The current-sourcing and-sinking capability of the CA3130
output stage is easily supplemented to provide power-boost
capability. In the circuit of Figure 17, three CMOS transistor-
pairs in a single CA3600E (see Note 12) lC array are shown
parallel connected with the output stage in the CA3130. In
the Class A mode of CA3600E shown, a typical device
consumes 20mA of supply current at 15V operation. This
arrangement boosts the current-handling capability of the
CA3130 output stage by about 2.5X.
The amplifier circuit in Figure 17 employs feedback to
establish a closed-loop gain of 48dB. The typical large-signal
bandwidth (-3dB) is 50kHz.
NOTE:
9. See file number 619 for technical information.
7
4
6
3
2
R
1
100kΩ
R
2
100kΩ
R
3
100kΩ
ON-PERIOD
ADJUST
1MΩ
2kΩ 2kΩ
OFF-PERIOD
ADJUST
1MΩ
+15V
0.01µF
OUTPUT
2kΩ
0.001µF
0.01µF
0.1µF
1µF
S
1
CA3130
+
-
FIGURE 15. PULSE GENERATOR (ASTABLE MULTIVIBRATOR)
WITH PROVISIONS FOR INDEPENDENT CONTROL
OF “ON” AND “OFF” PERIODS
FREQUENCY RANGE:
POSITION OF S
1
0.001µF
0.01µF
0.1µF
1µF
PULSE PERIOD
4µs to 1ms
40µs to 10ms
0.4ms to 100ms
4ms to 1s
CA3130, CA3130A
