This simple general-purpose transistor mixer was taken from an article in Electronics Now magazine in March 1994. You can choose a low-noise transistor such as the BC549.
This circuit is from a Maxim manual and can be used to power shields from batteries. The circuit...
In the figure we have an inductance bridge for values between 1 and 30 uH at a frequency of 5 MHz....
For those who have multimeters that do not test transistors, in the figure we have a circuit that...