Transistor Amplifier Circuits

Here is a very simple BC549C transistor amplifier circuit using an LT700 Transformer to drive a loudspeaker. If you are using The Little Whippersnapper's Crystal Radio system and need a simple circuit to drive the loudspeaker, then this will work. Enjoy!

Biased Transistor Circuit

Here is a perfectly biased transistor amplifier circuit for use in an electronics project. It is biased for precise mid-point operation at 4.5 V, when the power to the circuit is at 9 V. This makes an ideal second stage or third stage amplifier circuit to amplify audio signals. For the transistor, you could use any of the general-purpose NPN transistors such as the BC549, BC548, or BC547.