Highly linear VHF current-mode Miller integrator with 90 dB DC gain

This paper presents a concept and an implementation of a current-mode integrator based on the Miller effect. The circuit has a highly linear, no feedback, current path, implemented using a Gilbert amplifier cell, and a voltage feedback path with capacitors, realizing integration. A bipolar transistor array process with devices with an f _T of 8 GHz has been used for the circuit simulation. Phase response of -90±0.5° has been obtained in the frequency range of 1 MHz to 670 MHz (the low-frequency pole can be tuned electronically down to about 3 Hz). Excess phase can be compensated electronically to obtain exactly -90° for any frequency in the entire useful range. The gain of the circuit can be tuned electronically over at least 40 dB. THD for 1 MHz is better than 0.052% for an output current of 2.8 mA_pp, which represents 93% of the output tail current. DC gain of the circuit can be turned up to over 90 dB