CA3140AMZ datasheet(13/24 Pages) RENESAS

13 / 24 page

CA3140, CA3140A

FN957 Rev.10.01

Page 13 of 21

Feb 19, 2026

This circuit can be adjusted most easily with a distortion analyzer,

but a good first approximation can be made by comparing the

output signal with that of a sine wave generator. The initial slope is

adjusted with the potentiometer R1, followed by an adjustment of

R2. The final slope is established by adjusting R3, thereby adding

additional segments that are contributed by these diodes.

Because there is some interaction among these controls,

repetition of the adjustment procedure may be necessary.

SWEEPING GENERATOR

Figure 13 shows a sweeping generator. Three CA3140s are used

in this circuit. One CA3140 is used as an integrator, a second

device is used as a hysteresis switch that determines the starting

and stopping points of the sweep. A third CA3140 is used as a

logarithmic shaping network for the log function. Rates and

slopes, as well as sawtooth, triangle, and logarithmic sweeps are

generated by this circuit.

WIDEBAND OUTPUT AMPLIFIER

Figure 14 shows a high slew rate, wideband amplifier suitable for

use as a 50

 transmission line driver. This circuit, when used in

conjunction with the function generator and sine wave shaper

circuits shown in Figures 10 and 12 provides 18VP-P output open

circuited, or 9VP-P output when terminated in 50. The slew rate

required of this amplifier is 28V/

s (18VP-P x  x 0.5MHz).

POWER SUPPLIES

High input impedance, common mode capability down to the

negative supply and high output drive current capability are key

factors in the design of wide range output voltage supplies that

use a single input voltage to provide a regulated output voltage

that can be adjusted from essentially 0V to 24V.

Unlike many regulator systems using comparators having a

bipolar transistor input stage, a high impedance reference voltage

divider from a single supply can be used in connection with the

CA3140 (see Figure 15).

Essentially, the regulators, shown in Figures 16 and 17, are

connected as non inverting power operational amplifiers with a

gain of 3.2. An 8V reference input yields a maximum output

voltage slightly greater than 25V. As a voltage follower, when the

reference input goes to 0V the output will be 0V. Because the

offset voltage is also multiplied by the 3.2 gain factor, a

potentiometer is needed to null the offset voltage.

Series pass transistors with high ICBO levels will also prevent the

output voltage from reaching zero because there is a finite voltage

drop (VCESAT) across the output of the CA3140 (see Figure 2).

This saturation voltage level may indeed set the lowest voltage

obtainable.

The high impedance presented by Terminal 8 is advantageous in

effecting current limiting. Thus, only a small signal transistor is

required for the current-limit sensing amplifier. Resistive

decoupling is provided for this transistor to minimize damage to it

or the CA3140 in the event of unusual input or output transients

on the supply rail.

Figures 16 and 17, show circuits in which a D2201 high speed

diode is used for the current sensor. This diode was chosen for

its slightly higher forward voltage drop characteristic, thus giving

greater sensitivity. It must be emphasized that heat sinking of

this diode is essential to minimize variation of the current trip

point due to internal heating of the diode. That is, 1A at 1V

forward drop represents one watt which can result in significant

regenerative changes in the current trip point as the diode

temperature rises. Placing the small signal reference amplifier in

the proximity of the current sensing diode also helps minimize

the variability in the trip level due to the negative temperature

coefficient of the diode. In spite of those limitations, the current

limiting point can easily be adjusted over the range from 10mA

to 1A with a single adjustment potentiometer. If the temperature

stability of the current limiting system is a serious consideration,

the more usual current sampling resistor type of circuitry should

be employed.

A power Darlington transistor (in a metal can with heatsink), is

used as the series pass element for the conventional current

limiting system, Figure 16, because high power Darlington

dissipation will be encountered at low output voltage and high

currents.

CA3140

F

25V

2.2



2N3053

1N914

2.2



1N914

2.7



2.7



2N4037

- 50F

25V

SIGNAL

LEVEL

ADJUSTMENT

2.5k



200



2.4pF

2pF

-15V

+15V

OUTPUT

DC LEVEL

ADJUSTMENT

-15V

+15V



200



1.8k



OUT

NOMINAL BANDWIDTH = 10MHz

tr = 35ns

FIGURE 14. WIDEBAND OUTPUT AMPLIFIER

CA3140

VOLTAGE

REFERENCE

VOLTAGE

ADJUSTMENT

REGULATED

OUTPUT

INPUT

FIGURE 15. BASIC SINGLE SUPPLY VOLTAGE REGULATOR

SHOWING VOLTAGE FOLLOWER CONFIGURATION

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