12 V – 120 V Inverter Circuit

Ever needed a low power 120volt AC power source for your car, van or truck? Well this circuit should do the trick for you. This is the design for the problem. The circuit will supply 15 watts of AC power to a device. The circuit should power lamps, shavers, small stereos and small appliances. This is the figure of the circuit.


If you draw to much power the circuit will shut down all by itself. The output of this circuit is a square wave so there may be some noticeable hum on audio units plugged into it. To reduce some of the hum increase the value of the output capacitor which is at .47uf now. That transistor in the circuit are high power PNP transistors. Radio Shack part number 276-2025 are good ones to use or TIP32. The transformer is a 24 volt 2 amp center tapped secondary Radio Shack part number 273-1512 or equivalent.

Adjustable Ratio Digital Divider Circuit

This circuit is allows a digital pulse input to be divided by any number from 1 to 100 with control provided by a single knob. The function of this circuit is ideal for bench type work where the rapid set-up and flexibility of the division ratio is highly desirable. When the circuit input is low, Q1 and Q3 are off and Q2 is on. This is the figure of the circuit.


When the input goes high Q2 goes off and Q1 turns on Q3. This causes Q3 to displace the 100 pF capacitor's charge into A1's summing junction. A1's output responds by jumping to the required value to maintain the summing junction at 0V. This sequence is repeated for every input pulse. During this time A1's output will form the staircase shape. When A1's output is great enough to just bias C1's ``a'' input below ground, C1's output goes low and resets A1 to 0V. [Circuit’s source: National Semiconductor Notes].