For oscillators which may be part of phase-locked loops (PLLs) or delay-locked loops (DLLs) and for logic signal delays which may be needed for matching and alignment, continuously variable directly are often required. Such delays are most useful if they have a delay value which is directly proportional to a control input voltage or current, if they have a wide delay range (extending down to a minimum delay time equivalent to the delay of one logic gate), and if they have rapid settling so that short pulse experience little width distortion. High-speed data communication systems have a need for such improved variable delay circuits, especially for use in making clock timing and in synchronizing data carried by high-speed data buses.