Push-pull Output Stage Research Articles

A High Slew-Rate Push–Pull Output Amplifier for Low-Quiescent Current Low-Dropout Regulators With Transient-Response Improvement

A high slew-rate amplifier with push-pull output driving capability is proposed to enable an ultra-low quiescent current (Iq ~ 1muA) low-dropout (LDO) regulator with improved transient responses. The proposed amplifier eliminates the tradeoff between small Iq and large slew-rate that is imposed by the tail-current in conventional amplifier design. Push-pull output stage is introduced to enhance the output driving ability. Small dropout voltage (Vbo) with large-size pass transistor and ultra-low Iq can thus be used to minimize power loss of LDO regulator without transient-response degradation. The proposed amplifier helps to improve stability of LDO regulators without using any on-chip and off-chip compensation capacitors. This is beneficial to chip-level power management requiring high-area efficiency. An LDO regulator with the proposed amplifier has been implemented in a 0.18- mum standard CMOS process and occupies 0.09 mm2. The LDO regulator can deliver 50-mA load current at 1-V input and ~ 100-mV VDO . It only consumes 1.2 muA Iq and is able to recover within ~ 4 mus even under the worst case scenario.

Current Mode Linear Driver for High Energy Physics Applications

A single-ended to differential linear current driver has been designed and implemented in a 0.25 mum CMOS technology. This full-custom cell is intended for analogue data transmission in large-scale High-Energy Physics (HEP) experiments in the future CERN's Large Hadron Collider (LHC). Intrinsic technology radiation tolerance and specific design methodologies qualify this device to operate over 10 years in the LHC high radiation environment. High linearity and low power-overhead are achieved through a local feedback input stage and a current push-pull output stage. Linearity error is less than 0.1% in the specified operating range and 1% in close to full-swing operation. Static, dynamic and noise performance have been proven to be stable after a total ionising dose of 20 Mrad (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and after accelerated annealing

An expandable on-chip BP learning neural network chip

An expandable on-chip back-propagation (BP) learning neural network chip is designed. The chip has four neurons and 16 synapses. Large-scale neural networks with arbitrary layers and discretional neurons per layer can be constructed by combining a certain number of such unit chips. A novel neuron circuit with programmable parameters, which generates not only the sigmoid function but also its derivative, is proposed. The neuron has a push-pull output stage to gain strong driving ability in both charge and discharge processes, which is very important in heavy load situations. An improved version of the Gilbert multiplier is also proposed. It has large linear range and accurate zero point. The chip is fabricated with a standard 0.5 μm CMOS, double-poly, double-metal technology. The results of parity experiments demonstrate its ability of on-chip BP learning.

An ECL gate with improved speed and low power in a BiCMOS process

An emitter-coupled logic (ECL) gate exhibiting an improved speed-power product over the circuits presented in the past is described. The improvement is due to a combination of a push-pull output stage driven by a controlled current source, thus reducing the static and increasing the dynamic current. This circuit has better driving capabilities and improved speed, yet it uses an order of magnitude less power than a regular ECL gate. Due to its reduced power consumption, this gate allows for a higher level of integration of ECL logic. The realization of this circuit using a regular bipolar process is also possible.

A monolithic quad line driver for industrial applications

The device described in this paper is a new quad line driver to be used in the hostile and noisy industrial environment and developed in mixed technology (BCD: Bipolar, CMOS, DMOS). It consists of four independent line drivers, each of which has a rail-to-rail push-pull output stage realized with power DMOS transistors connected in half bridge configuration. Even though the device is designed to be used primarily in the output cards of programmable controllers, it is a general purpose device, since it can drive any kind of load (resistive, capacitive, or inductive) with an output current of 100 mA. The novel structure of the top driver allows full protection of the output stage against any kind of short circuits and/or overloads, providing a linear current limitation. Furthermore, when a channel is tristated, for every applied voltage ranging from ground to the supply voltage, virtually zero current is absorbed from the output. An innovative high efficiency central charge pump circuit has also been designed and implemented, making both a very wide supply voltage operation (6-50 V) and high switching frequency (up to 500 KHz) possible, The device can also be used as a receiver since the input voltage can swing from -10-50 V.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Video CMOS power buffer with extended linearity

A CMOS power buffer suitable for video applications is discussed. The use of a high-speed push-pull output stage and a highly linear high-speed driver allows good linearity to be maintained even with very high input frequencies. Indeed, total harmonic distortions (THDs) as good as -66 and -58 dB are achieved at 0.5 and 1 MHz, respectively, with a load resistance of 75 Omega . The integrated prototype, realized using a 1.2- mu m CMOS process, occupies a silicon area of 280 mils/sup 2/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Extending voltage-mode op amps to current-mode performance

This paper reviews techniques for extending the output cababilities of conventional voltage-mode operational amplifiers to achieve current-mode performance. Tracing the development over the past two decades, a number of elegant and useful circuit topologies for realising amplifiers with controlled current output properties are described. In particular, the operational amplifier supply current sensing technique and its application to current follower and current conveyor circuit implementations is examined. The authors then review their work, based on enhancing the performance of conventional voltage-mode amplifier designs by application of these currentmode alternatives.A high performance follower based amplifier, a biquadratic filter section, a precision full-wave rectifier and an instrumentation amplifier based upon enhancement to the voltage operational amplifier are shown to outperform their conventional counterparts. The integrated circuit realisation of a seven terminal operational amplifier that allows direct access to the operational amplifier output current via its push-pull output stage is then presented. The integrated seven terminal operational amplifier is realised in CMOS technology and experimental results presented. Finally a current feedback, high precision, current gain cell is described that overcomes several of the drawbacks that exist with the supply current sensing technique.

Sub-300-ps CBL circuits

Advanced charge-buffered-logic (CBL) circuits featuring double-poly self-alignment, a 'free' epi-base lateral p-n-p (cutoff frequency=300 MHz only), and deep trench isolation are discussed. Using 1.2- mu m design rules and a modified push-pull output stage, a gate delay (fan-in=3) of 278 ps was obtained at a DC current of 30 mu A/gate. The low power-delay product underlies the speed and power potential of CBL as an attractive practical approach to bipolar complementary transistor logic.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design of a high-gain, single-stage operational amplifier for GaAs switched-capacitor filters

The letter describes the design of a single-stage, double cascode amplifier for GaAs switch-capacitor filters. The amplifier achieves a voltage gain of 60 dB assuming a realistic low-gain model for the N-channel GaAs DFETs employed. The need for compensation is avoided using a single-stage architecture, and a push-pull output stage minimises power consumption and chip area.

High-voltage technology offers new solutions for interface integrated circuits

A BIMOS IC technology improving the design of interface circuits that require either high-voltage (up to 120 V) of current (up to a few amperes per output) has been developed. Both bipolar and MOS complementary components are processed together on the same chip for low- and high-voltage applications. Various BIMOS power interface circuits are now in production, e.g., a motor driver, a high-voltage plasma display driver, and a printer head driver. This paper describes the BIMOS technology and the characteristics of its components. As applications, two circuits are presented: the UEB 4732 (plasma display driver) with complementary MOS push-pull output stages (120 V), and the UAA 2081 (stepper motor driver) with power bipolar transistors (1 A per output). Both circuits have a logical part designed with low-voltage CMOS (5-12 V).

Large swing CMOS power amplifier

A CMOS class AB power amplifier is presented in which supply-to-supply voltage swings across low-impedance loads are efficiently and readily handled. The amplifier consists of a high-gain input stage and a push-pull unity-gain amplifier output stage. The amplifier dissipates only 7 mW of DC power and delivers 36 mW of AC power to a 300-/spl Omega/ load, using standard power supplies of /spl plusmn/5.0 V. Lower impedance loads can be driven to higher power levels, providing the internal current limiting level is not exceeded.

Hi-fi philosophy from a European point of view

The paper deals with popularizing hi-fi listening facilities in Europe which, due to a difference in broadcasting practice is easier over there than in the United States. These differences are analyzed and the conclusion of the writer is that a large contingent of hi-fi listeners in Europe could be created by improving the reproduction quality of fm radio sets without increasing the cost too much. As a distortion limit for this purpose a figure of 1 per cent is chosen, while the output power should be near the 10-watt figure. To realize these properties a special circuit has been designed viz., a single-ended push-pull output stage with combined positive and negative feedback. A loudspeaker with a voice coil impedance of 800 ohms is being used, making an output transformer superfluous. This direct coupling is one of the necessities to get a cheap but very good setup. Further, the so-called 3D system and means for getting rid of the keyhole effect are discussed.

A new full-wave magnetic amplifier output stage

THOSE concerned with the development of high-performance magnetic amplifier servo systems have long recognized the need for an output stage which would produce a full-wave current output into a servomotor and still retain the two inherent advantages, namely, the high speed of response and demodulation of the half-wave amplifier. In this paper a new concept in full-wave push-pull output stages is presented which fulfills this need. Test data are given to show its operation in an actual system.

A New Circuit for balancing the Characteristics of Pairs of Valves

IN circuits containing balanced valves, as used in such applications as push-pull output stages or in d.c. amplifiers, it is customary to balance the valves by means of external circuit adjustments so that errors caused by differences in their characteristics are reduced. There are various methods of doing this1; but none of these gives compensation for all characteristics simultaneously, as it is possible to make adjustments to only one of the three properties, namely, zero balance (equality of static plate currents), stage gain and effect of changes of cathode-supply voltage.

An A.C. Operated D.C. Amplifier with Large Current Output

The theory and design of an a.c. operated d.c. amplifier with large current output are presented. A d.c. phase inverter using cathode in-phase degeneration drives the push-pull output stage. The output is linear over a range of 160 ma.