Microwave HBT circuits for frequency synthesisers

The aim of this paper is to show how the GaAs/GaAlAs heterojunction bipolar transistor (HBT) can be used in extending the range of digital circuit operation to microwave frequencies. The paper will also touch on the design techniques used with the HBT in tackling circuits at high frequencies. The particular application which will be used in demonstrating the HBT´s capabilities are circuits for a microwave frequency synthesiser. In this paper the reasons for the high operating speed of the HBT will be briefly explained before showing how the design of the high speed circuits was undertaken. Experimental results are then given on high speed counters and prescalers