Low-noise CMOS signal processing IC for interpolating cathode strip chambers

A CMOS circuit for obtaining precision amplitude and timing information from the cathodes of a proportional chamber with interpolating cathode strips has been developed. The chip performs charge amplification, shaping, analog storage and multiplexing, and generates a prompt timing pulse which can be used for trigger purposes. Novel features of the IC include: preamplifier optimized for large (40-250 pF) detector capacitance, digitally programmable gain and bandwidth of the fourth-order shaper, and an array of on-chip capacitors and switches for injecting charge for calibration. Noise is less than 1500 RMS electrons with an input capacitance of 100 pF using bipolar 550 nsec shaping. Linearity is better than 0.8% over a dynamic range of 1500:1. The constant fraction discriminator has a time walk of ±2.5 nsec over the range 10-500 fC. Power dissipation is 50 mW per channel