Abstract: A delta-sigma modulator comprises a 1-bit quantizer located for quantizing an analog signal applied thereto, and for outputting a first quantized digital signal, a 1-bit DA converter converting the first quantized digital signal into a quantized analog signal, a subtracting circuit for subtracting the quantized analog signal output from the 1-bit DA converter from the analog signal input to the 1-bit quantizer, and an input integrating circuit series including a series of one or more stages each of which includes a subtracter and an integrator for integrating an output of the subtracter, one subtracter at a first stage subtracting the quantized analog signal delayed by a delay element from an input analog signal input to the delta-sigma modulator, and one integrator at a final stage outputting its output to the 1-bit quantizer. A multiple-bit quantizer quantizes an analog output of the subtracting circuit and outputs a second quantized digital signal.

Abstract: In a sample hold circuit (6, 50, 60) capable of relaxing a dependency of a voltage of an analogue input signal on an ON resistance of a switch (2). In the sample hold circuit (6, 50, 60), plural reference voltages VrefN are supplied, and unit switches (11e) forming the switch (2) are selectively activated (an ON state) based on a comparison results (whether or not the voltage of the analogue input signal is greater than each reference voltage) from plural comparison circuits (13e) whose operations are performed based on the voltage of the analogue input signal (1).

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 multi-bit D/A converter which improves the linearity of an analog output relative to a digital input is provided. A switch control circuit (1) turns on D some of a plurality of switches (S1 to SM) which are arranged in ascending order starting with a switch determined by a start position determination circuit (3) and turns off the remaining switches, the number of switches turned on being dependent on a digital signal (DIG). The start position determination circuit (3) sequentially changes the switches (S1, S3, S5, . . . ) serving as a selection start position to determine the selection start position for each input of the digital signal (DIG) provided in synchronism with a clock signal (CLK).

Abstract: An A/D converter includes a sample-hold circuit, A/D converting stages connected in series to the sample-hold circuit, and an encoder/latch circuit which adds 3-bit digital signals issued from the A/D converting stages to each other for outputting a signal of 9 bits. The sample-hold circuit and the A/D converting stages each include a differential amplifier. Differential outputs of each differential amplifier are short-circuited for a predetermined initial period in each sampling period.

Abstract: An object is to obtain a voltage comparator capable of high-accuracy voltage comparison. An input voltage (VIN) and a reference voltage (VREF) are connected to one electrode of a capacitor (C1) through switches (S1) and (S2), respectively. The other electrode of the capacitor (C1) is connected to the input portion of an inverter (INV1). The output portion of the inverter (INV1) is connected to the input portion of an inverter (INV3) and is also fed back to the input through a switch (S3). An inverter (INV11) is further connected in parallel with the inverter (INV1), wherein the input/output characteristics of the inverters (INV1, INV3 and INV11) are set equal.

Abstract: In a pipeline type A/D converter, a switch for sampling an analog potential signal has its other terminal in connection with an A/D converter, a D/A converter, a capacitor for subtraction. Even when frequency of the analog potential signal is raised such that input current is increased and a voltage drop is increased at the switch, there will be no error in the result of subtraction like in the conventional example where analog potential signal was directly input to A/D converter. Accordingly, a pipeline type A/D converter with low power dissipation and satisfactory frequency characteristics is obtained.

Abstract: A ladder resistance (1) consisting of resistance elements (r1, r2, . . . , r8) connected in series with intermediate taps (T1, T2, . . . , T7) interposed is so arranged as to be folded back at its midpoint. Pairs of differential comparators (C1 and C7, C2 and C6, . . . ) which are connected to common intermediate taps are each disposed adjacently so as to be nearest to the intermediate tap to be connected thereto. Accordingly, wires connecting the differential comparators (C1, C2, . . . , C7) to the intermediate taps (T1, T2, . . . , T7) become shorter and an area of a semiconductor chip needed for arranging the wires can be reduced. Thus, reduction in area of the semiconductor chip needed for providing the device therein is achieved.

Abstract: In a pipeline type A/D converter, a sample/hold.cndot.subtracter circuit of an A/D converter block of a first stage samples an analog voltage and outputs an offset voltage at a first phase, and subtracts an output voltage of an A/D converter from the sampled analog voltage in a second phase. An A/D converter of an A/D converter block of a succeeding stage subtracts the output voltage of the sample/hold.cndot.subtracter circuit of the first phase from the output voltage of the sample hold.cndot.subtracter circuit of the second phase, and converts the subtracted result into a digital code. The influence of an offset of a differential amplifier included in the sample/hold.cndot.subtracter circuit is removed so that A/D conversion of high accuracy is allowed.

Abstract: An A/D converter block A/D1 converts an analog input signal Vin to a digital signal and outputs its D/A output. First SH/SUBT7, 8 sample the signal Vin and a voltage VRM at the same timing with said A/D conversion and output the results of subtraction of the respective sampling values and the D/A output during holding, respectively. The both results of subtraction are several tens mV and there is no need of taking account of the linearity of a differential amplifier DIFF11. During the sampling, a circuit SHR1 outputs the differential voltages between each reference tap voltage taken out from specific 2 points of the ladder-type resistor in the A/D converter block A/D1 and the voltage VRM while a differential amplifier DIFF12 applies the reference voltages to the next A/D converter block A/D2. Such operations are performed in each stage. Thus, it becomes possible to make any S/H circuit and amplifier of excellent linearity in the first stage unnecessary to reduce the electric power consumption.

Abstract: A high-performance differential latch circuit which includes a differential amplifier circuit comprised of an NMOS transistor (27) serving as a constant current source, PMOS transistors (3, 4) and NMOS transistors (23,24), a latch circuit comprised of NMOS transistors (25, 26), and a switch circuit comprised of NMOS transistors (21,22,28) for alternately operating the differential amplifying function and latch function, the transistor (27) serving as the constant current source having a drain terminal directly connected to the transistors (23,24) and a source terminal directly connected to a ground voltage (2), whereby the differential latch circuit differentially amplifies the signals without the loss of the constant current source function during the differential amplification.

Abstract: There is disclosed an A-D converter testing circuit wherein exclusive-OR gates (13a, 13b) provide the exclusive-OR of the high-order bits (D.sub.1a, D.sub.1b) of the outputs of A-D converters (12a, 12b) and the exclusive-OR of the high-order bits (D.sub.1b, D.sub.1c) of the outputs of A-D converters (12b, 12c), respectively, and an OR gate (13c) provides the logical sum of the outputs of the both gates, which is "L" if all of the bits (D.sub.1a, D.sub.1b, D.sub.1c) are equal. A tri-state buffer (15a) receives the output of the OR gate (13c) at its control end and receives the bit (D.sub.1c) at its input. When all of the A-D converters are normal, all of the bits (D.sub.1a, D.sub.1b, D.sub.1c) are equal and are applied to the output of the tri-state buffer (15a). When one or some of the A-D converters are abnormal, the output of the tri-state buffer (15a) enters a high-impedance state. The A-D converter testing circuit, therefore, rapidly judges whether the A-D converters are defective or non-defective.

Abstract: Voltage comparators C.sub.1 -C.sub.N for comparing a first differential reference voltage obtained by dividing a first reference voltage V.sub.RT and a second reference voltage V.sub.RB by ladder resistors r.sub.1 -r.sub.N+1 and a second differential reference input voltage formed by a third voltage V.sub.i and a fourth voltage V.sub.i are arranged in first to N/2 and (N/2+1)-th to N-th voltage comparator rows in a folded manner and wiring area can be reduced as a result.

Abstract: An upper comparator group compares an analog signal with upper reference potentials applied from upper ladder resistance network. A switch group outputs the predetermined intermediate reference potential of the ladder resistance network to an analog subtracting circuit in response to the upper comparison results. The analog subtracting circuit subtracts the intermediate reference potential from the analog signal for producing an input signal for use in the lower side. A lower ladder resistance network outputs lower reference potentials obtained by dividing by resistors constant static intermediate reference potentials of the ladder resistance network applied from a differential amplifying circuit. A lower comparator group compares the lower reference potentials with the input signal for lower comparison. The upper and the lower comparison results are converted into a digital signal by upper and the lower encoders and the adding/subtracting circuit.

Abstract: In order to obtain a constant current circuit which has an excellent constant current property and requires no plural bias circuits, a base of an NPN bipolar transistor (5) and a gate of an N-channel MOS transistor (6) are connected to a first terminal (1) in common. A collector of the transistor (5) is connected to a second terminal (2) and a source of a transistor (6) is connected to a third terminal respectively, while a voltage source (59) is connected between the first and third terminals. An emitter of the transistor (5) is connected with a drain of the transistor (6). Identical bias voltages are supplied to the base and the gate, while a gate-to-drain voltage of the transistor (6) is equal to a base-to-emitter voltage of the transistor (5). Thus, the transistor (6) operates in a pentode region, to serve as a constant current load for the transistor (5).

Abstract: Disclosed is a high-speed A/D converter (15) including an improved differential amplifier circuit. Each comparator (61) provided in the A/D converter directly receives a complementary or differential analog input voltage to be converted. A differential amplifier circuit provided in each comparator compares an applied analog input voltage difference and an applied reference voltage difference. A binary signal indicative of a comparison result is applied to an encoder (4) through a binarization circuit. An analog input voltage which is not to be converted is directly applied to the comparator, that is, to the differential amplifier circuit through none of resistor elements and components, whereby conversion time delay is prevented.

Abstract: The present invention is directed to improvement of a differential amplifier an its peripheral components employed in an A/D converter to enhance an accuracy of the A/D converter. The differential amplifier has an amplifying element comprised of a pair of differential transistors Q1 and Q2, emitter resistances 2a and 2b, and collector resistances 2c and 2d. The differential amplifier has transistors Q3 and Q4 constituting an emitter follower for applying an output amplified in the differential amplifying element to the outside. The differential amplifier includes transistors Q5 and Q6 having their respective base electrodes connected to input terminals 4a and 4b and serially connected to the transistors Q3 and Q4, and resistances 2e and 2f interposed between emitter electrodes of the transistors Q5 and Q6 so as to relieve any influence of variations in base-emitter voltages of the transistors Q3 and Q4.

Abstract: Positive and negative output ends of a differential circuit in a sample hold circuit are connected to capacitors through switch circuits. Further, collectors of two input transistors of a buffer circuit connected to the sample hold circuit are driven by a collector driving differential circuit, so as to make the collector.multidot.base voltages of two input transistors same to each other. Consequently, a stable sample hold circuit having an arbitrary gain can be provided. In addition, drifts of outputs from two capacitors in the sample hold circuit can be made equal to each other by the buffer circuit.

Abstract: In order to improve linearlity of analog current outputs with respect to input digital codes in a D-A converter formed by a matrix array of unit current sources, respective current source cells forming the matrix are connected by analog ground wires (101 to 105 ) along respective rows. Analog ground wires (301, 302 ) connect left sides of the analog ground wires (102, 104) and right sides of the analog ground wires (101, 103, 105) to pads (41, 42 ) respectively, to ground the same. Thus, large-small relations of current distributions are reversed in respective rows, whereby influences by the current distributions are cancelled.

Abstract: An A/D converter main body is formed in the form of an annulus with a wiring region set as its center, and a ladder resistor array for dividing an input reference voltage and an analog signal line for applying an input analog signal to each comparator in the A/D converter are formed in the form of an annulus with the wiring region set as a center. Wirings from terminals are once concentrated into the wiring region by an input/output line group and then distributed therefrom to circuit elements. Since the ladder resistor array is formed in a circular form, resistance values are less liable to change as compared to the case where the ladder resistor array is bent, resulting in a higher precision of reference voltages for comparison. Further, wiring lengths for control signals to be applied to the circuit elements are made equal, and there is no fear of line delays in the control signals.