Implementation of triangle wave generator circuit based on single chip MAX9000

The good linearity of the triangle wave makes the triangle wave generator very useful in many "scanning" circuits and test equipment. For example, switching power supplies and induction motor control circuits require a triangle wave generator to implement pulse width modulation (PWM).

This article describes how to use a single MAX9000 IC and several passive components to implement a simple triangle wave generator. The MAX9000 integrates a high-speed op amp, a high-speed comparator, and a precision bandgap reference.

Circuit Description

Figure 1. Basic circuit of a triangle wave generator.

Figure 2. Triangle wave generator implemented using the MAX9000.

Figure 1 shows the basic circuit of a triangle wave generator, which includes two functions: an integrator for generating a triangle wave output and a comparator (Schmitt trigger) with external hysteresis for controlling the triangle wave amplitude.

The operational amplifier is configured as an integrator to generate a triangular wave. The basic principle is to generate a linear ramp voltage by integrating a constant voltage. The integrator output is fed back to its inverting input through a Schmitt trigger. The input threshold voltage of the Schmitt trigger is set according to the peak voltage of the triangular wave.

However, the circuit shown in Figure 1 has a disadvantage. The peak voltage of the triangle wave must be symmetrical with the reference voltage at the inverting input of the comparator. If you want to generate a triangle wave from 0.5V to 4.5V, you need a reference voltage of (0.5V + 4.5V)/2 = 2.5V. Since the output voltage of the standard bandgap reference is 1.23V, it is best to set the triangle wave output voltage independently of the reference voltage. The resistor R3 added to the hysteresis network in Figure 2 can help achieve this function. After using R3, the peak value of the triangle wave output by the MAX9000 is no longer affected by the reference voltage.