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A circuit technique for compensating the device-to-device variation in Bandgap voltage references is presented. The circuit senses the variation of V be of the transistor with process and pumps into the emitter a PTAT current in direction opposite to the variation to bring it back to the right value. It also exploits the temperature coeff. of MOS V t to compensate for higher order temperature variations. Silicon results show a variation of 60mV across different lots and less than 50 PPM across temperature (-40 o C to 130 o C) .The prototype was built in a 0.18u CMOS digital process with low β PNP transistors.

The authors propose two single amplifier low pass filter topologies achieving a second order roll-off in a transimpedance (i-to-v) configuration. Both topologies are derived with the constraint of fully differential signal processing. A transimpedance configuration finds direct application in scenarios when the input signal is in current domain while the output needs to be a voltage. Output of a current steering DigitalAnalog converter, and output of a down-conversion mixer, are two such examples. The transimpedance active-RC configurations presented here achieve the desired filtering with a single op-amp while eliminating redundant voltage conversion. Thus, immense advantages in terms of noise, linearity and area are obtained. To the best of authors' knowledge, no one has previously reported single amplifier bi-quadratic active-RC topologies in fully differential transimpedance configuration.

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