A low level amplifier with a 700 MHz bandwidth

A beam-lead sealed-junction silicon air-isolated-monolithic (AIM) low level amplifier has been developed with a closed loop gain of 13 dB terminated by 50 ohm input and output impedances. The low frequency and high frequency 3 dB points are below 20 KHz and above 700 MHz, respectively. The amplifier is a three-stage transistor feedback amplifier with diode bootstrapping. A common emitter stage is followed by two cascaded emitter followers with bootstrapping between the first stage collector and the second stage emitter. The transistors are 4 to 5 GHz silicon devices with an fmaxof 7 to 12 GHz. The devices have 2.5 micron stripes and spacings with a base width of about 0.20 micron. The series-connected forward biased bootstrapping diodes consist of the emitter-base junction of the transistors with the collector shorted to the base. Diffused bias resistors are included in the AIM circuit. Amplifiers have been fabricated with a 13 dB gain and 1.0 GHz bandwidth. In going from an ambient temperature of 25°C to 60°C, the gain deviation is tess than 0.1 dB and the phase deviation is less than 2° up to 300 MHz.