Ft doubler
![](http://w140.com/tekwiki/images/thumb/5/56/Ft-doubler-circuit.jpg/350px-Ft-doubler-circuit.jpg)
The ft doubler circuit is a transistor amplifier topology, invented by Carl Battjes, that has a current gain of 2 even at the transit frequency of the transistors that are used in the circuit.
It is used heavily in Tektronix instruments and several Tektronix integrated circuits implement this approach.