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Introduction The TL494 is arguably one of the most successful and iconic integrated circuits (ICs) in the history of power electronics. Introduced by Texas Instruments in the late 1970s, this fixed-frequency, pulse-width modulation (PWM) control IC has stood the test of time. From inexpensive computer power supplies (PSUs) in the 1990s to modern inverter circuits, battery chargers, and DC-DC converters, the TL494 remains a favorite among hobbyists and professional engineers.
Whether you are building a 500W inverter for a camping trip, a laboratory power supply, or a solar charge controller, the TL494 remains a reliable, well-documented workhorse. Bookmark this guide, buy a few ICs, and build the circuits above—starting with the simple oscillator test, then moving to the buck converter. Once you see that clean PWM waveform on your oscilloscope, you will understand why this 1970s IC refuses to retire. For further study, download the official Texas Instruments TL494 datasheet (SLVS074G). It contains 20+ reference designs that directly match the circuit diagrams discussed here. tl494 circuit diagram
| Pin # | Name | Function | | :--- | :--- | :--- | | 1 | Non-Inverting Input (Error Amp 1) | Usually connected to the voltage feedback. | | 2 | Inverting Input (Error Amp 1) | Connected to a reference voltage. | | 3 | Feedback/PWM Comp | Common point for compensation networks. | | 4 | Dead-Time Control (DTC) | Voltage here controls dead time (0V to 3V). | | 5 | CT | Capacitor for timing oscillator. | | 6 | RT | Resistor for timing oscillator. | | 7 | GND | Ground. | | 8 | C1 | Collector of Output Transistor 1. | | 9 | E1 | Emitter of Output Transistor 1. | | 10 | E2 | Emitter of Output Transistor 2. | | 11 | C2 | Collector of Output Transistor 2. | | 12 | VCC | IC Supply Voltage. | | 13 | Output Control | Selects mode: High = Push-pull, Low = Single-ended. | | 14 | REF | 5V Precision Reference Output. | | 15 | Inverting Input (Error Amp 2) | Usually used for current limiting. | | 16 | Non-Inverting Input (Error Amp 2) | Connected to current sense shunt. | Introduction The TL494 is arguably one of the
The oscillator (pins 5 & 6) generates a sawtooth wave. The PWM comparator compares this sawtooth to the error signal from Amps 1 & 2. The output logic then drives the two transistors (Q1/Q2). Pin 4 (DTC) adds an offset to the sawtooth, limiting max duty cycle. Essential TL494 Circuit Diagrams Below are three practical schematics. Component values are included for common frequencies (typically 50kHz to 100kHz). Diagram 1: Basic PWM Generator (Test Rig) Before building a power supply, build this simple test circuit to verify your TL494 works. It outputs complementary square waves without feedback. Whether you are building a 500W inverter for