Praween Sinha, Ajay Shankar, Mohit Arora and Mohit Datta 54 International Journal of Emerging Trends in Electrical and Electronics (IJETEE) Vol. 1, Issue. 3, March-2013. Design and Implementation of Low Voltage, High Bandwidth MOS Current Mirrors Praween Sinha, Ajay Shankar, Mohit Arora and Mohit Datta 4 Abstract: Design of current mirrors that can operate at higher frequency ranges is an important and growing field. This paper presents a modification to the conventional current mirrors, in the form of a precisely controlled resistance between the gates of the MOSFETs in order to achieve current mirroring at higher frequencies. Both passive and active realization techniques for the resistance have been considered in the improved current mirror. Likewise, to facilitate the operation of a current mirror at lower biasing voltages at the output, level-shifter technique has also been implemented. I. Introduction: In the typical IC design, biasing is often achieved by using a constant current source. Usually, this current is obtained by using a MOSFET biased to saturation, but generating separate drain currents whose values are free of process and temperature dependencies is not possible even if a known gate to source voltage is used[1]. Hence this is achieved by generating one constant and reliable current source and copying its value at different locations in the circuit. Current mirrors are employed for this purpose. Not only do they find extensive applications in almost all analog and mixed mode circuitry, their applications in analog signal processing circuits in communication systems[2] make improvement of their bandwidth an important field of study. A Wilson current mirror is commonly used because of its good accuracy and output impedance[3]. Its operating bandwidth, although a bit higher than cascode configurations[4], can still be improved. A MOS Wilson mirror takes the circuit of Figure 2. Applications of current mirrors in circuits operating at higher frequencies require suitable modifications because the present designs show high losses as the operating frequency is increased. In order to facilitate the use of mirrors at frequencies extending well into the microwave frequency ranges, a modification, in the form of a resistor between the gate terminals of the MOSFETs M1 and M2, has been considered. Level shifter configurations have been implemented for low voltage operation of mirrors. Praween Sinha is serving as Assistant Professor at Maharaja Agrasen Institute of Technology, New Delhi, India, Ajay Shankar, Mohit Arora and Mohit Datta are pursuing B.Tech (final year) in Electronics and communication engineering at Maharaja Agrasen Institute of Technology , New Delhi , India, Emails: praweenrsinha@rediffmail.com , ajayshankar@outlook.com , mohit.arora2013@gmail.com , datmoh.9@gmail.com The paper is organized as follows. Section 1 deals with the simple current mirror and two modifications to it. A method for improvement of bandwidth for Wilson mirror has been presented in section 2. Section 3 presents low voltage operation circuit for a general and Wilson mirror. 1. Simple Current Mirror A simple current mirror circuit replicates the input current of a current source and a current sink as the output current. However, the replication accuracy is poor due to channel length modulation effects. The bandwidth of this mirror is also very low. It is a first order low-pass filter with its cut-off frequency given by[5]: ω o = ୥୫ ଶେ୥ୱ (i) Figure 1 1. Passive Compensation: The introduction of a compensation resistor between the gates of M1 and M2 [6], as shown in Fig.1, transposes the first-order low-pass current mirror to a second-order low-pass mirror with one zero and two poles. The bandwidth is given as: ω o= ට ୥୫ଵ ோ஼௚௦ଵ஼௚௦ଶ (ii) Thus by choosing R=1/g m and C gs1 =C gs2 =C gs , the bandwidth is given as g m /C gs which is twice the bandwidth as compared to uncompensated current mirror. 2. Active Compensation: A diode-connected enhancement type MOSFET is used as an active compensation[7] resistance which tracks the trans-conductance which varies with process and temperature drifts.