Very Wide Range Tunable CMOS/Bipolar Current Mirrors with Voltage Clamped Input

In low power current mode signal processing circuits it is many times required to use current mirrors to replicate and amplify/attenuate current signals, and to clamp the voltage of nodes with high parasitic capacitances so that the smallest currents do not introduce unacceptable delays. The use of tunable active-input current mirrors would meet both requirements. In conventional active input current mirrors stability compensation is required. Furthermore, once stabilized, input current cannot be made arbitrarily small. In this paper we introduce two new active-input current mirrors that clamp their input node to a given voltage. One of them does not require compensation, while the other may require under some circumstances, but for both input current may take any value. The mirrors can operate with their transistors biased in strong inversion, weak inversion or even as CMOS compatible lateral bipolar devices. If biased in weak inversion or as lateral bipolars, the current mirror gain can be tuned over a very wide range. According to the experimental measurements provided in this paper, input current may spawn beyond nine decades, and current mirror gain can be tuned over 11 decades. As an application example a sinusoidal gm-C based VCO has been fabricated whose oscillation frequency could be tuned for over 7 decades between 74mHz and 1MHz.