Topology and size optimization methods are used to design compliant mechanisms that produce a constant output force for a given actuator characteristic of linearly decreasing force versus displacement. The design procedure consists of two stages: (i) topology optimization using two-dimensional (2-D) continuum parametrization, and (ii) size optimization of the beam-element abstraction derived from the continuum topology solution. The examples considered are based upon electrostatic microactuators used widely in microsystems. The procedure described here provides conceptual as well as practically usable designs for compliant transmission mechanisms with a constant output force characteristic. For any given topology design, the maximum achievable constant force over a given displacement range is determined. Ideal rigid-body and spring-equipped mechanisms are analyzed and their features are used to compare with the compliant solutions obtained.