Motorola Corporation

Other

Semiconductor Components Industries, LLC

Robert L Vyne

Thomas D Petty

David M Susak

Troy L Stockstad

Richard S Griffith

William F Davis

Robert N Dotson

Renwin J Yee

Thomas A Somerville

Rikki Koda

Robert Bruce Davies

Alexander Wayne Hietala

Jefferson W Hall

Bradley T Moore

John F Casey

David W Feldbaumer

Gary L Spraggins

Petr Kadanka

Chad Traylor

A self compensating operational amplifier (,) including a differential amplifier input stage (,) and a current mirror (,) having an input and an output coupled to the respective outputs (,) of the differential amplifier input stage is provided that uses a feedback amplifier (,) which senses any voltages differences between the input and outputs of the current mirror as current is sourced or sank at the output (,) of the operational amplifier. The feedback amplifier produces a feedback current to the input side (,) of the current mirror wherein the voltage at the input side of the current mirror tracks the voltage swing at the output side of the current mirror so that the voltages track and are substantially matched.

DC gain enhancement for operational amplifiers

A comparator circuit (10) with hysteresis having transistors with the same threshold voltage and a method for comparing input signals. The comparator circuit (10) includes a current mirror (11) coupled to a common electrode differential pair (12) and to a feedback circuit (13). The current mirror (11) has a large output impedance and provides a plurality of output currents (I.sub.21, I.sub.26, I.sub.31). Some (I.sub.21, I.sub.26) of the currents are transmitted to the common electrode differential pair and one (I.sub.31) of the currents is transmitted to the feedback circuit (13). The output currents (I.sub.21, I.sub.26, I.sub.31) are modulated to generate positive feedback signals that control changing the output state of the comparator circuit (10) as well as provide hysteresis for the comparator circuit (10).

Comparator circuit and method

A bandgap reference circuit (60) provides a selectable bandgap reference voltage that is substantially insensitive to temperature variations of an operating reference circuit. A final curvature caused by a current (I.sub.2) in a temperature coefficient compensation transistor (40) is equal to a drift in a Vbe voltage of a transistor (18) having a negative temperature coefficient plus the drift in a Vbe voltage of a transistor (20) having a positive temperature coefficient minus the drift in a Vbe voltage of the temperature coefficient compensation transistor (40). The nonlinearity of the current (I.sub.2) in the temperature coefficient compensation transistor (40) is adjusted by selecting a compensating current and associated temperature coefficient for the compensating current (I.sub.0) to minimize the characteristic bow or curvature of the current (I.sub.2) in the temperature coefficient compensation transistor (40).

Bandgap reference circuit and method

Low voltage operational amplifier (10) operates in a voltage range of one to eight volts over a temperature range of 0.degree. to 70.degree. centigrade. Op amp input stage (12) uses N-channel depletion-mode MOSFETs to provide amplification of the differential input and maintain constant transconductance. Source follower MOSFET (13) provides unity gain in transferring the AC signal, STAGE-1 OUTPUT, to the base of current sinking transistor (18). Sink control circuit (14) and source control circuit (22) generate the base drive currents for in transistors (18) and (24). The signal at the output of MOSFET (13) either causes the sink transistor (18) to sink current or the signal to be transposed by means of a translinear loop (16) and causes the source transistor (24) to source current.

Low voltage operational amplifier bias circuit and method

Low voltage operational amplifier (10) operates in a voltage range of one to eight volts over a temperature range of 0.degree. to 70.degree. centigrade. Op amp input stage (12) uses N-channel depletion-mode MOSFETs to provide amplification of the differential input and maintain constant transconductance. Source follower MOSFET (13) provides unity gain in transferring the AC signal, STAGE-1 OUTPUT, to the base of current sinking transistor (18). Sink control circuit (14) and source control circuit (22) generate the base drive currents for transistors (18) and (24). The signal at the output of MOSFET (13) either causes the sink transistor (18) to sink current or the signal to be transposed by means of a translinear loop (16) and causes the source transistor (24) to source current. An output stage provides approximately fifty milliamps of current drive and is quiescent until the output driver is selected.

Low voltage operational amplifier input stage and method

A trim circuit (10) and method of reducing offset voltages in a differential input stage. The differential input transistors (32 and 42) have separate bulk terminals for receiving a voltage to compensate for the input offset voltage. A current source (60) supplies a static current to the offset compensation circuit for generating a bias voltage at node (55). The transistors (64 and 66) receive a voltage at input terminals (30 and 40) and supply an additional current to an offset compensation circuit (20). A switch circuit (50) has switch pairs (52, 56, and 54, 58) for transferring a voltage to the bulk terminal of one of the differential transistors (32 and 42) while grounding the bulk terminal of the other transistor. The differential voltage supplied across the bulk terminals of transistors (32 and 42) changes the threshold voltage of the transistors reducing the offset voltage of the input stage.

Method and circuit for reducing offset voltages for a differential input

Low voltage operational amplifier (10) operates in a voltage range of one to eight volts over a temperature range of 0.degree. to 70.degree. centigrade. Op amp input stage (12) uses N-channel depletion-mode MOSFETs to provide amplification of the differential input and maintain constant transconductance. Source follower MOSFET (13) provides unity gain in transferring the AC signal, STAGE-1 OUTPUT, to the base of current sinking transistor (18). Sink control circuit (14) and source control circuit (22) generate the base drive currents for transistors (18) and (24). The signal at the output of MOSFET (13) either causes the sink transistor (18) to sink current or the signal to be transposed by means of a translinear loop (16) and causes the source transistor (24) to source current.

Low voltage operational amplifier and method

A modification circuit (30) is thermally coupled to and electrically isolated from a circuit element (20) of a utilization circuit (10). During modification, current pulses are passed through an isolation circuit (40) to the modification circuit which heats the circuit element, e.g., a resistor, of the utilization circuit substantially above the normal operating temperature range of the element, thereby modifying the electrical characteristics of the resistor and therefore those of the utilization circuit to which it is connected. During normal operation of the utilization circuit the circuit element of the utilization circuit is electrically isolated from the modification circuit.

Circuit and method of modifying characteristics of a utilization circuit

A band-gap voltage reference (39) has a regulator portion (70) providing a substantially constant current of predetermined magnitude Ic and a band-gap reference portion (72) receiving Ic. The reference portion (72) has a first branch including a first transistor (52) of a first type serially coupled to a second transistor (55) of a second type, a second branch including a third transistor (53) of the first type serially coupled to a fourth transistor (56) of the second type, the first and second branches forming a current mirror (73) carrying a total current of about Ic/2, and a third branch (57) in parallel with the first and second branches and carrying a current of substantially Ic-Ic/2. Base current (65) in the first two branches is compensated by base current (64) of the third branch.

Electrical apparatus and method for providing a reference signal

A voltage regulator (11) having an input (12) for receiving an input current and an output (13) for providing a regulated voltage. The voltage regulator (11) comprising a diode (14), a capacitor (16), a first comparator (17), a second comparator (18), a logic circuit (19), and a switch circuit (21). The capacitor (16) is charged by the input current coupled through the diode (14). The first comparator (17) senses when the voltage on the capacitor (16) exceeds a first reference voltage and provides a signal to the logic circuit (19). The logic circuit (19) enables the switch circuit (21) for shunting the input current from charging the capacitor (19). The second comparator (18) senses when the voltage on the capacitor (16) falls below a second reference voltage and provides a signal to the logic circuit (19). The logic circuit (19) disables the switch circuit (21) from shunting the input current thereby charging the capacitor (19). Thus, the voltage at output (13) stays between the first and second predetermined voltages.

Voltage regulator and method therefor

An amplifier circuit (10) receives a differential input signal and provides an amplified differential signal. A converter circuit (14) is responsive to the amplified differential signal and provides a single-ended signal. An output stage (16) is responsive to the single-ended signal for providing an output signal of the amplifier circuit. The output stage provides bias cancellation for the single-ended signal by injecting a current equal to the bias requirement of the input transistors (20, 38). The bias cancellation maintains a high input impedance and high gain and output drive for the output stage.

Amplifier having an output stage with bias current cancellation

A TC controlled RF signal detecting circuitry (211) used in the output power control circuit of a TDMA RF signal power amplifier includes positive coefficient current source (303) producing current I+ having a positive TC, negative coefficient current source (305) producing current I- having a negative TC, and current mirror (301) for summing currents I+ and I- to produce substantially identical compensated mirror currents Im1 and Im2. Anti-clamping current mirror (309) mirrors current Im2 to produce compensated currents Ia1 and Ia2, which are applied to and bias a Schottky diode coupled in series to a resistor network in each leg of diode detector (311). Each leg of diode detector (311) has a positive TC, which is substantially offset by the negative TC of compensated currents Ia1 and Ia2. Schottky diode (431) in one leg of diode detector (311) half-wave rectifies RF feedback signal (212) to produce temperature and voltage compensated power level signal (229), which has a DC level proportional to the output power level of RF output signal (214). By using TC controlled RF signal detecting circuitry (211), power level signal (229) has a DC level which is stable to within 5 mV over temperature ranging from -55.degree. C. to +125.degree. C. and over power supply voltage ranging from 2.7 V to 4.75 V.

Temperature-coefficient controlled radio frequency signal detecting

An input stage to an amplifier circuit (10) operating with a one volt power supply potential (32) receives a differential input signal. A charge pump (36) increases the one volt power supply potential to 1.8 volts for providing additional head-room for the differential input signal. A current source (44) controls a current mirror (40-42) to draw a predetermined current from the charge pump to supply the active conduction path of a differential transistor pair (12-14). An output stage (34) of the amplifier circuit operates off the one volt power supply potential. Since the charge pump drives only the differential transistor pair through the current mirror, it may be made small to fit on the same integrated circuit as the amplifier including any necessary pump capacitors.

Amplifier input stage with charge pump supplying a differential

A pulsed battery charger circuit (11) for charging a battery (28). A control circuit (17) is responsive to a sense circuit (16) that monitors the battery voltage. The control circuit (17) pulses a first current source (25) or a second current source (20). An amplifier (14) is responsive to the first (25) and second (20) current sources for generating first and second predetermined voltages between a drive output (12) and a sense input (13). The first current source (25) is pulsed when the sense circuit (16) senses the battery voltage to be less than a first threshold voltage. The second current source (20) is pulsed when the sense circuit (16) senses the battery voltage to be greater than the first threshold voltage. Both the first (25) and second (20) current sources are disabled when the sense circuit (16) senses the battery voltage to be greater than a second threshold voltage.

Pulsed battery charger circuit

A high impedance output driver stage (16) for reducing loading on a gain stage (18) which drives an output stage (19). The output stage (19) is responsive to an input current. A current sense circuit (21) senses current of output stage (19). The current sense circuit (21) outputs a current proportional to the current sensed in the output stage (19). A current source circuit (22) is responsive to the current output by the current sense circuit (21) and outputs a current substantially equal to the input current of the output stage (19) thereby reducing loading on the gain stage (18).

Growing community of inventors

Tempe, AZ, United States of America

Robert L Vyne