High resolution track and hold for broadband wireless applications

The purpose of this paper is to describe and compare GaAs-InGaP HBT high sample rate track and hold amplifier designs. These are building blocks targeted to be used in next generation data conversion circuits. The track and hold designs are optimized to operate at 600 MSPS with 10 bits effective resolution. The two designs were fabricated to accommodate 0.5 Vpp and 1.0 Vpp full-scale voltage swings. The design with input signal requirement of 1.0 Vpp generates second and third harmonic distortion below -74 dBc at 60 MHz during single-tone test. During two-tone measurements, the device generated third order intermodulation distortion of -72 dBc with carriers centered around 61 MHz and -54 dBc with carriers close to Nyquist frequency. With a full-scale swing of 4.0 Vpp, the device generated third harmonic distortion of -45 dBc at 60 MHz input frequency. The pedestal during hold is less than 1 mV and droop rate is negligible. The designs were fabricated utilizing Nortel Network´s GaAs-InGaP HBT with f/sub t/ of 70 GHz and fmax of 110 GHz.