Kabushiki Kaisha Toshiba

Tokyo Shibaura Denki Kabushiki Kaisha

Shouji Abou

Itsuo Sasaki

Yasoji Suzuki

Kenji Matsuo

Keiko Chikaoka

A voltage controlled oscillator includes an oscillator having at least one first capacitor. The oscillator receives first and second input voltages and charges the first capacitor with a first current corresponding to the first input voltage. The oscillator oscillates at a frequency corresponding to the first and second input voltages. To remove the adverse influence on the oscillating frequency by the change of process parameters caused in the stage of manufacturing the voltage controlled oscillators, a second capacitor is charged for a predetermined period by a current corresponding to the first voltage. After the charging of the second capacitor ends, a sample/hold circuit samples and holds the charged voltage across the second capacitor. An operational amplifier receives, at its positive input terminal, the output voltage of the sample/hold circuit, and, at its negative input terminal, the reference voltage. The operational amplifier controls the first voltage so that the output signal of the sample/hold circuit will be equal to the reference voltage. Repeating the sequence of the charging, sampling and comparing operations eliminates the influence upon the oscillating frequency by the change of the process parameters caused in the manufacturing stage.

Voltage controlled oscillator having frequency independent of process

An input MOS transistor receives an input voltage and produces a current corresponding to the input voltage. A charge/discharge circuit charges a capacitor alternately in two different directions by the output current of the transistor. A select circuit alternately selects and produces one of the potentials at either of the electrodes of the capacitor. A single two-input comparator compares a reference potential with a potential of the output signal of the select circuit. The select circuit produces a signal corresponding to the comparison result. The select circuit allows the output signal of the comparator to be transmitted alternately to the set input terminal and the reset input terminal of a flip-flop. The flip-flop is set and reset by the output signal of the switch means to produce an oscillating signal. According to a change in the level of the oscillating signal, the charge/discharge circuit switches the charging direction of the capacitor. According to a change in the voltage level of the output signal of the flip-flop, the select circuit selects the potential which is higher in absolute value than the other. According to a change in the voltage level of this output signal, the switch circuit directs the output signal of the comparator to one of the set and reset input terminals of the flip-flop.

Voltage controlled oscillator using flip-flop controlled switching

Disclosed is a switched capacitor filter circuit employing the equivalent resistance of a switched capacitor circuit as the resistive element in a frequency dependent impedance converting circuit.

Switched capacitor filter circuit

A signal corresponding to an analog input signal is supplied to one of two input terminals of a two-input, one-output MOS differential amplifier. A reference voltage signal is supplied to the other of the two input terminals of the MOS differential amplifier. A bipolar transistor having one end connected to an analog signal output terminal is driven by a signal from the output terminal of the MOS differential amplifier. A loudspeaker is driven by the bipolar transistor.

Analog signal power amplifier circuit

A MOS power amplifier circuit comprised of a load driver including two p-channel MOSFETs connected in series, a preamplifier for amplifying an analog input signal and supplying the amplified one to the gate of one of the MOSFETs and for rendering the impedance of the two MOSFETs low; and an inverting amplifier for invert-amplifying the output signal from the preamplifier and supplying the amplified one to the gate of the other MOSFET. The operating voltage of the preamplifier and the inverting amplifier is higher than that of the load driver.

MOS Power amplifier circuit

An operational amplifier having a differential amplifier section, a level shifting section, an output section and a bias section. In the operational amplifier, the bias section senses any changes in the power voltage and controls the level shifting of the level shifting section with the sensed change in the power voltage so as to remove an offset component in the output voltage of the differential amplifier section which arises from the power voltage change.

Growing community of inventors

Kawasaki, Japan

Shouji Abou