Analysis of High Frequency Square Wave Signal Isolation and Power Amplification

Abstract

When designing circuits, it is often unavoidable to mix digital and analog signals. Considering electromagnetic compatibility, then the digital signal must be separated from the analog signal. However, for complex systems, complete separation of the two is difficult to achieve. When the digital signal current (assuming the digital signal frequency is large) flows through the analog signal circuit, the ground current of the digital signal will form a large loop. The high frequency current flowing through the loop will produce radiation and a very high ground inductance. When the analog signal current (assuming the analog signal is at a low level) flows through the digital signal circuit, the analog signal ground current will form a large loop. The analog current flowing through this loop will be interfered by the digital signal. Therefore, it is necessary to consider the method of signal isolation. Based on the above considerations, this paper introduces a method to isolate high frequency square wave signals using optocoupler isolation. Not only that, when the driving switch is a high-power switch, the signal generated by a general signal generator cannot drive the switch directly. Therefore, power amplification of the signal is required. This paper also provides a power amplifier circuit based on the class B push-pull power circuit topology. Finally, a power amplifier circuit for optocoupler isolation of digital signals with frequencies up to 100 kHz is proposed.