RF Linear Hybrid Amplifiers
Posted Jul 28th 2011
A new class of low cost, high performance hybrid amplifiers has emerged to assist the design engineer working in the frequency range of 1 to 500 MHz. Utilizing the low distortion and wide dynamic range performance technology developed for the CATV industry, these amplifiers feature power output capabilities previously unavailable in hybrid circuits.
RF linear hybrid amplifiers represent a new family of medium power, broadband gain blocks for multi purpose RF applications. Internally matched at both the input and the output for either 50 ohm or 75 ohm systems, these devices cover gains ranging from 17 to 35 dB, and can accommodate output power levels in excess of 400 mW. Linear class A bias conditions accommodate third order intercept values in excess of + 45 dBmV. Depending on quantity and model selected, most prices fall in the range of $30. to $60. If you’ve been using transistors like the 2N3866, 2N5109, or stud mounted devices, read on. You may save a lot more than just design time.
RF linear hybrid amplifiers utilize the thin film manufacturing and construction techniques developed for the demanding CATV industry. All ceramic substrates are alumina (A1203) with gold conducting paths. Resistors are either cermet or nichrome, and are laser trimmed to better than one percent tolerance. For maximum MTBF, gold metallized transistor die are used incorporating resistive ballasting in the emitter fingers to provide even thermal distribution across the surface corporating resistive ballasting in the emitter fingers to provide even thermal distribution across the surface of the die and to eliminate “hot spotting.” These transistor die are subjected to rigorous testing through an extensive wafer qualification program before being mounted on the circuit. The hybrid manufacturer must insure that the transistors used will meet the exacting requirements for gain, distortion, and noise figure.