Abstract: In a variable frequency divider formed of a latch train, a frequency division ratio is set through selective invalidating a feedback signal to a first stage latch from the last stage latch. A size of MOS (metal-insulator-semiconductor) transistors for switching the division ratio is made larger than that of other MOS transistors in differential stages in the last stage latch circuit. Further, differential signals are transmitted as feedback signals to the first stage latch circuit. A F/(F+1) prescaler which operates stably with a low current consumption under a low power supply voltage condition is implemented.

Abstract: An object is to obtain a semiconductor in which the body potential can be externally fixed with a body potential fixing portion and in which no semiconductor region where ions of different conductivity types are mixed exists. A semiconductor layer (10) on an insulating layer (20) has an under semiconductor layer (10b) under an element isolation portion (14) and a body (10a) under a closed-loop portion (150). A gate structure (15) has gate pads (151) and the closed-loop portion (150). While a body potential fixing portion (13) is located on the opposite side of the element isolation portion (14) from the gate structure (15), the gate structure (15) is formed from the semiconductor layer (10) to extend on the element isolation portion (14). Accordingly, the body potential fixing portion (13) can be connected to the body (10a) through the under semiconductor layer (10b) without through the pn junction formed by the source (12) and the semiconductor layer (10).

Abstract: An object is to obtain an amplification circuit which provides a high gain even with a low-voltage power supply. The amplification circuit comprises an MOS transistor (M1) having a gate receiving an amplified signal (RFin), a source electrically connected to ground, and a drain electrically connected to a supply voltage (VDD), wherein the back gate-source voltage (Vbs) of the MOS transistor (M1) is made larger as the gate-source voltage (Vgs) of the MOS transistor (M1) becomes larger, thereby making the threshold voltage (VT) of the MOS transistor (M1) smaller.

Abstract: An A/D converter simplifies its circuit configuration without deteriorating accuracy in A/D conversion. A circuit is formed of a folding and interpolation type. A gain-variable pre-amplifier group 11 amplifies each of reference voltages Vref1 to VrefN and an analog input voltage Vin, to output the result to a folding amplifier group 12, while a gain-variable pre-amplifier group 21 amplifies each of reference voltages Vrr1 to VrrJ and the analog input voltage Vin, to output the result to a comparator group 24. Each of pre-amplifiers constituting the gain-variable pre-amplifier groups 11 and 21 has an amplification factor that varies in upper and lower comparison periods according to a clock control signal .PHI.cnt.

Abstract: A phase shifter is provided between common emitters of two differential transistor pairs of a mixer circuit. The phase shifter changes the phase of a voltage signal input to one common emitter by 180.degree. and applies it to the other common emitter, and causes a current in accordance with the voltage between the common emitters. As compared with the prior art employing two stages of vertically connected differential transistor pairs, the power supply voltage can be reduced.