Abstract

Transimpedance amplifiers provide a high dynamic range and wide bandwidth over that obtained using high impedance amplifiers.¹ However, most InP-based integrated optical receivers demonstrated today use high impedance amplifiers. This is because the integrated high-impedance amplifiers are easy to characterize. Another reason is due to the relatively low transimpedance observed for the integrated transimpedance amplifiers, which is attributed to the low value of the integrated feedback resistor.² The integrated resistor is commonly fabricated using the FET channel layer because of its simplicity for integration with other FETs in the circuit. However, such resistors with a high value of resistance consume a large area which can result in a large parasitic shunt capacitance and inductance. Here we describe an In_0.53Ga_0.47As JFET transimpedance amplifier, which consists of a common source inverter stage, a level-shift buffer stage, and a narrow-gate transistor³ (5µm wide and 30µm long) as an active feedback resistor. The output resistance of the narrow-gate transistor operated in its linear region can be dynamically tuned over a wide range. Moreover, the device can be made very small to reduce parasitic capacitance and inductance.

© 1990 Optical Society of America