HIGH-IMPEDANCE CURRENT SOURCE USES GAAS-MESFETS

IMPEDANCE levels provided by GaAs metal semiconductor field effect tra nsistors (MESFETs) are inherently limited by the device's low output c onductance, with impedance levels of a few hundred ohms or less being typical. When combined with other circuitry (such as differential ampl ifiers), the low impedance from the current source results in a large differential-gain imbalance. A novel current-source design for an inte grated MESFET process achieves high impedance at RF frequencies while allowing for implementation within a small die area.