Stewart S. Taylor

A high-performance GaAs pin electronics circuit for automatic test equipment

A GaAs MESFET pin electronics circuit suitable for automated test equipment (ATE) has been designed and tested. A driver, window comparator, and programmable load have been integrated on a single chip. The driver has a variable amplitude of 0 to 7 V, a variable rise/fall time of 250 ps to 5 ns, and a 50- Omega output impedance. The driver has a real-time high-impedance inhibit mode that disconnects and reconnects on the fly at rates equal to the data rate, which is greater than 1 Gb/s. Additionally, the voltage compliance of the driver in inhibit mode exceeds the high and low output levels by any amount within the -4-V to 7-V compliance window. Pattern dependent delay is typically +or-50 ps. The two comparators operate over the same compliance window with a dispersion in propagation delay of less than 100 ps for an overdrive of greater than 100 mV. The comparators have a high input impedance, low bias current, and show no evidence of oscillation when being overdriven by slow dV/dt input signals. The programmable load provides a sinking capability of greater than 50 mA over the compliance range. >

A GaAs MESFET Schottky diode barrier height reference circuit

This barrier height reference circuit consists of a voltage loop containing a Schottky diode voltage, V/sub d/, and the difference in voltages of an even number of Schottky diodes, /spl Delta/V. The diode difference voltage is established by operating two groups of diodes at different current densities. This circuit is, in a sense, a bandgap reference and its operation is similar to that of a conventional bandgap reference. The circuit is implemented in a low-power, ion-implanted, GaAs MESFET manufacturing process.

A high-performance GaAs pin electronics chip for high-speed general purpose ATE

A GaAs pin electronics circuit with a driver, window comparator, and programmable load has been integrated on a single chip. The driver has a variable amplitude of 0 to 7 V, a variable rise/fall time of 250 ps to 5 ns, and a 50 ohm output impedance. The driver has a real-time, high impedance tristate mode (inhibit) which disconnects and reconnects on the fly at rates equal to the data rate (>1 Gb/s). Additionally, the voltage compliance of the driver in tristate mode exceeds the high and low output levels by any amount within the -4 V to 7 V compliance window. Pattern-dependent delay is typically less than 50 ps. The two comparators operate over the same compliance window with a dispersion in propagation delay of less than 200 ps for an overdrive of greater than 100 mV.<<ETX>>

A 2pAspl radic/Hz 622 Mb/s GaAs MESFET transimpedance amplifier

Telecommunication systems require high sensitivity transimpedance amplifiers with wide dynamic range for loopback testing. Although GaAs MESFET technology has superior noise performance compared to silicon technology for transimpedance amplifiers, this has not been fully exploited. Low voltage gain, which leads to a small feedback resistor, and the use of numerous active devices that have significant channel noise degrades the noise performance of many designs. Silicon bipolar transimpedance amplifiers suffer from poor sensitivity because of the shot noise produced by the base current, and from the thermal noise produced by a low-value feedback resistor. A low-value feedback resistor can result from the parasitic capacitance associated with implanted or thin-film resistors, and the lossy silicon substrate. This parasitic capacitance lowers the bandwidth because it exists in the feedback path with the feedback resistor and/or because it degrades stability. GaAs MESFET technology, on the other hand, does not suffer from this limitation because of the semi-insulating substrate. The challenge for GaAs MESFET technology is to produce adequate voltage gain in spite of the low inherent gain of short-channel MESFETs without degrading noise performance or stability. The circuit described here meets these requirements and achieves an average input-referred noise current of <2pAspl radic/Hz over 500 MHz bandwidth. Self-contained AGC extends dynamic range without external components.<<ETX>>

Silicon vs GaAs for personal communication RF ICs

Presents a summary on silicon versus GaAs for personal communication RF ICs. The panelists explain what level of performance is needed and why one technology is more suitable than the other.<<ETX>>

Design considerations for GaAs MESFET RF power amplifiers

Practical aspects of low-voltage, 1–3 watt RF power amplifiers for wireless phones will be presented, particularly as they relate to GaAs MESFET integrated circuits. Device, package, and circuit approaches will be reviewed. Typical performance of GaAs MESFET power amplifiers for 840MHz cellular AMPS & TDMA, 1900MHz PCS TDMA, and DCS 1800 will be presented.