Current-mode Amplifier Research Articles

Constant-bandwidth current mode operational amplifier

A current mode operational amplifier with a low impedance output for feedback connection is proposed and analysed theoretically. It is found to have a constant bandwidth independent of the gain in a closed loop configuration. This property is due to the loop gain independent of the closed loop gain. The amplifier is shown to be composed of a current conveyor input stage and another current conveyor output stage. Experimental results are presented to verify the constant bandwidth performance, and it is concluded that the proposed configuration is suitable for high frequency current mode amplifiers.

Current-controlled translinear impedance converter

A current-controlled impedance converter is described which is implemented using two translinear active devices: a current conveyor with unity gain and an adjustable differential current-mode amplifier. It has low parasitic input impedance and useful properties when the amplifier gain is near unity. To characterize the circuit, SPICE simulation results are given and discussed.

Feedback Control of Impact Dynamnics of a Moving-Coli Actuator

A tracking feedback control method is used to enhance the throughput of a moving-coil print actuator (MovAcc). A ``double-pulse'' test is conducted to study the effect of initial conditions on actuator performance as measured by the repeatability of flight time and impact force. Experimental data presented as a family of normalized histograms show significant reduction in the flight-time and impact-force variation when feedback control is used. The controller realized using analog electronic components is a lead-lag compensator. The inputs to the controller are the actual position measurement of the MovAcc derived from an inexpensive optical sensor and a reference signal obtained from a waveform generator. The output of the controller drives a power op amp configured as a current-mode amplifier which in turn drives the MovAcc. The measured transfer function of the actuator shows the presence of higher order modes that may lead to an unstable closed-loop system. By limiting the frequency bandwidth of the closed-loop system, a Wellbehaved time response is obtained. Finally, a modified controller that allows ballistic dynamics of the MovAcc to dominate during the impact phase of the motion is shown to provide the best compromise between conventional operation and closed-loop control.

Novel bipolar differential input/output current-controlled current source

A new bipolar differential input/output current-controlled current source (CCCS) is described. The basic cell consists of a translinear array of six transistors with two bipolar inputs, and is suited for the input stage of a differential current-mode operational amplifier.

Circuit for Liquid Level Measurements Using Carbon Resistors

Current mode amplifier circuit used with carbon resistors for measuring low flow rates of liquid hydrogen from small containers