The paper presents the structure and the principle of operation of the improved' Howland current pumps (or voltage-controlled current sources (VCCSs) for a grounded load). In particular, under review is the VCCS employing power operational amplifier (op amp) and the VCCS using low power op amp and an additional power transistor, extending working dynamic range. On the basis of analysis of the operational principle, the equations for transfer functions of both circuits and formulas for the related dynamic electrical parameters are obtained. Moreover, using these formulas, a design procedure is developed, and recommendations for simulation modelling are given. The efficiency of the proposed procedure is verified by simulation modelling and experimental testing of sample electronic circuits of VCCSs. Copyright (c) 2013 John Wiley & Sons, Ltd.