Modification of basic speed control circuit for small DC permanent-magnet motors provides maximum current limit under normal conditions and reduced current limit under stall conditions, to limit dissipation of series transistor Q4, to safe value. When motor stalls, motor voltage falls, reducing voltage and motor current required to turn on Q3 and thereby limiting stalled-motor current,-D. Zinder, Current Limit and Foldback for Small Motor Control, EDN Magazine. May 5, 1974, p 77 and 79.
Required Field 
