A.C. van der Woerd

General current-mode analysis method for translinear filters

Log-domain or translinear filters are regarded as being a promising alternative in the area of low-voltage filter design. To date, most publications have reported on synthesis of translinear filters. Although synthesis is more powerful than analysis, it must go together with a generally applicable analysis method in the same domain. In this paper, a general current-mode analysis method is proposed. By using a current-mode approach, we stay close to the existing theory on static translinear circuits, which might be beneficial in developing a general, possibly more powerful synthesis method.

An RMS-DC converter based on the dynamic translinear principle

Translinear or log-domain filters are theoretically exact realisations of linear differential equations. However, the dynamical translinear principle can also be applied to the implementation of nonlinear differential equations. In this paper, an RMS-DC converter is proposed, comprising a direct implementation of the corresponding nonlinear differential equation by means of the dynamical translinear principle. Correct operation of the circuit was verified through measurements.

A low-voltage low-power fully-integratable automatic gain control for hearing instruments

A low-voltage low-power bipolar automatic gain control (A.G.C.) that works in the current domain and operates on a single 1.3-V battery is presented. In this A.G.C. a large time constant (50 ms) is realised on-chip. The A.G.C. consists of a gain cell, a comparator and a voltage follower. The active circuitry of the A.G.C. has been integrated in the DIMES01 process and the total circuit demonstrates operation down to 1 V with 4¿W power consumption.

Application of the back gate in MOS weak inversion translinear circuits

Though the MOS transistor is a four-terminal device, it is most often used as a three-terminal device. Therefore, a large number of possible MOS circuits are overlooked. In this brief, the four-terminal point of view is elaborated with respect to MOS weak inversion translinear circuits, a class of circuits naturally very suitable for low-voltage and low-power applications. Some new circuits are described which sometimes are more suitable for low-voltage applications than bipolar translinear networks performing the same function. It is also shown that, using the back gate, translinear networks can be derived which cannot be realized with bipolar transistors. These network topologies increase the possibilities offered by translinear technology. As an example, measurement results of a low input-voltage current mirror and a sin(x)-circuit are shown.

A low-voltage ultra-low-power translinear integrator for audio filter applications

In this paper, the design and measurement of a l-V translinear integrator and its application in a controllable second-order lowpass filter for hearing instruments is presented. A semicustom version of the filter has been integrated in a standard 2-/spl mu/m, 7-GHz, bipolar IC process and operates at voltages down to 1 V, consumes only 6 /spl mu/A, and has a dynamic range of 57 dB for a total harmonic distortion below 2%. Its cutoff frequency is linearly adjustable in octaves from 1.6 to 8 kHz.

A wide-tunable translinear second-order oscillator

This paper describes the design and measurement of a translinear second-order oscillator. The circuit is a direct implementation of a nonlinear second-order differential equation and follows from a recently developed synthesis method for dynamic translinear circuits. It comprises only two capacitors and a handful of bipolar transistors and can be instantaneously controlled over a very wide frequency range by only one control current, which indicates its suitability for spread-spectrum communications. Its total harmonic distortion can be made small by design, which enables fully integrated transmitters. A semicustom test chip, fabricated in a standard 2-µ, 7-GHz, bipolar IC process, operates from a single supply voltage, which can be as low as 2 V and oscillates over 6 decades of frequency with -31 dB total harmonic distortion.

A syllabic companding translinear filter

A distortionless syllabic companding filter can be obtained theoretically by updating the state variables of the filter as a function of the compression signal. In translinear filters, this is accomplished by adding a compensation current to all the capacitors in the filter. This current can be generated using only one capacitor and one transistor. Simulation results of a translinear syllabic companding differential filter are presented.

Nonlinear analysis of noise in static and dynamic translinear circuits

For translinear filters, or log-domain filters, calculation of the maximal signal-to-noise-ratio, an important filter specification, is not trivial, due to the inherent companding behavior and the nonstationary nature of the transistor noise sources. To address this issue, a nonlinear noise analysis method is proposed. Based on large-signal calculations, expressions for the first-order noise and signal-noise intermodulation terms are computed. The procedure is generally applicable both to static and dynamic translinear circuits, as illustrated by a number of generic examples.

A low-voltage low-power fully-integratable front-end for hearing instruments

In this paper, the core of a universally applicable analog integrated circuit for hearing instruments is presented: a microphone preamplifier and an input-controlled automatic gain control with an adjustable knee level. The test chip demonstrates operation down to 1.05 V and a current consumption between 80 and 125 ¿A. The full-custom chip area in a 2.5¿m BiCMOS process (using only vertical NPNs and lateral PNPs) amounts to 0.56 mm2.

Low-voltage low-power controllable preamplifier for electret microphones

A low-voltage low-power analog controllable preamplifier for electret microphones is discussed. It has been designed for a single supply voltage of 1.0 V, whereas its average power consumption amounts to some tens of microwatts. A DC current controls its gain directly into decibels. The design meets specifications concerning accuracy, bandwidth, and noise properties suitable for most applications in portable telephone equipment, portable transceivers, and hearing aids. Much attention has been paid to the dynamic range of the input signal, noise, and offset properties. The circuit has been realized in a semicustom IC process. Simulation and measurement data of the most important properties are presented. >