Need a small amplifier to amplify a radio front-end, or similar? This will do it! It produces up to 200mW into 8 ohms (at 12VDC) and 300mW into 4 ohms (at 12VDC). It's not powerful, no, but is similar to amplifiers used in clock radios, portable radios and cassette players, etc. This is a simple Class-B amplifier with a gain of 101, using an NE5532 op-amp as the heart. This is nowhere near Hi-Fi, but it's designed to drive those 56mm - 75mm speakers that are found in clock radios, etc. The input sensitivity is around 50mV for full output; so, if you wanted to present a 500mV input signal, and find the gain is too much; R5 could be reduced to 47k, to give a gain of 48. This amplifier could also be used as a headphone amplifier, if you so wanted. Or, even a signal tracer! Have fun!

Video on this build: