Triangular-Wave Generator Circuit

This is a circuit for a constant amplitude triangular-wave generator. A variable frequency triangular wave whose amplitude is independent of frequency is provided by this circuit. This circuit is based on LM101. This is the figure of the circuit;

As a reset circuit, the generator embodies an integrator as a ramp generator and a threshold detector with hysteresis. There is no further explanation is needed because the integrator has been described in a previous section. It’s a latch circuit with a large dead zone, on that case, the threshold amplifier detector is similar to a Schmidt Trigger. By using positive feedback around an operational amplifier, we can implement this function. The positive feedback network provides a voltage at the non-inverting input which is determined by the attenuation of the feedback loop and the saturation voltage amplifier when the amplifier output is in either the positive or negative saturated state. The voltage at the input of the amplifier must be caused to change polarity by an amount in excess of the amplifier input offset voltage to cause the amplifier to change states. When this is done, until the voltage at its input again reverse, the amplifier saturates in the opposite direction and remains in that state. By examining the operation with the output of the threshold detector in the positive state, the complete circuit operation may be understood. To cause a current I+ to flow, we have to apply the detector positive saturation voltage to the integrator summing junction through the combination R3 and R4.

Then, a negative-going ramp with a rate of I+/C1 volts per second until its output equals the negative trip point of the threshold detector is generated by the integrator. After that, at the integrator summing point , the threshold detector changes to the negative output state and supplies a negative current, I-. A positive-going ramp with a rate of I-/C1 volts per second is generated by the integrator until its output equals the positive trip point of the threshold detector where the detector again changes output state and the cycle repeats. R3, R4, C1, and the positive and negative saturation voltages of the amplifier A1 determine the triangular-wave frequency. Amplitude is determined by the threshold detector saturation voltages and the ratio of R5 to the combination of R1 and R2. If the detector has equal positive and negative saturation voltages, positive and negative ramp rates are equal and positive and negative peaks are equal. If the inverting input of the threshold detector, A1, is offset with respect to ground, the output waveform may be offset with respect to ground. If the detector is clamped with matched Zener diodes as shown in following figure, the generator may be made independent of temperature and supply voltage. If power supply impedance causes oscillation during its transition time, the detector may be compensated and the integrator should be compensated for unity-gain. For maximum symmetry, the current into the integrator should be large with respect to Ibias and offset voltage should be small with respect to Voutpeak.

[Schematic circuit source: National Semiconductor Application Note]

Telephone Ring Generator Circuit

This is circuit that produces a ring generator will ring a telephone once every 10 seconds. The interval between rings can be lengthened or shortened by varying the value of the 1 Mega Ohm of resistor. Here’s the circuit schematic.


This circuit is using small power transformer. The 70 volt/ 30 Hz ring voltage is produced from the 120 volt side of a small 12.6 VAC power transformer (Radio Shack 273-1365). Both capacitors connected across the transformer windings are non-polarized / 100 volts. Circuit draws about 300mA from the 12 volt DC power supply during the ringing interval. This circuit is controlled by 556 timer IC.

Square Wave Generator Using CMOS 74C14 Single Integrated Circuit Chip

Many ways to create a square wave output, but by far the simplest is to use a CMOS Hex Schmitt trigger inverter. These are fast, and with the outputs in parallel, will provide enough drive to ensure that the rise and fall times are very short indeed. This is one design circuit for the square wave generator. This is the figure.


This circuit is based on CMOS IC 74C14. The output of this circuit is from 0V to +12V, and is fed to the 10k level pot by a 10k resistor. This reduces the level to 6V P-P, which is equal to 3V RMS. The input circuit is designed to ensure that the Schmitt input is supplied from a 1/2 supply voltage (6V), so the applied AC will swing evenly about this point and produce a symmetrical square wave.

Broadband Random Noise Generator Circuit

This circuit is often needed in testing any type of electronic systems such as filter, audio, or RF communication. The circuit presented here generates an RMS amplitude regulated noise source with selectable bandwidth. This circuit is work based on op amp. This is the figure of the circuit.


With 1 KHz to 5 MHz decade ranges selectable bandwidth and 300mV RMS output, this noise generator is suitable for wide range of application. Noise is generated by D1 that is AC coupled to A2, an amplifier with broadband gain 100. The output of A2 is fed to a simple selectable low-pass filter. The filter’s output is applied to LT1228 operational trans-conductance amplifier A3. A3’s output feeds current feedback amplifier LT1228 A4. A4’s output, which is also the circuit’s output, is sampled by the A5-based gain control configuration. This closes a gain control loop to A3. A3’s ISET current controls gain, allowing overall output level control.