When the mixed translinear loop is used in a voltage follower implementation the value of its output resistance depends on its bias current. This property is used in the realization of a current controlled conveyor (CCCII), which has therefore its serial resistance on port X controlled by the bias current. The two basic implementations, that allow from a CCCII and without additive resistances to realize controlled voltage-current converters, are described. A current-controlled voltage-amplifier and a current-controlled current-amplifier are then analyzed. They are implemented from only two CCCIIs and do not require any passive component. The principal implementations for current controlled first-order transfer functions, operating either in voltage-mode or in current-mode, are introduced. They require one or two of the preceding controlled conveyors and use capacitors only. SPICE simulation results, obtained using the parameters of the HF3CMOS process from SGS THOMSON, are given for the CCCII and for its main applications. They confirm the validity of the theoretical analyzes and also underline the high frequency potential of the current controlled implementations introduced. A second-order bandpass filter, operating in voltage-mode, is also described. It is obtained from CCCIIs and two capacitors only. Its centre frequency, which is adjustable by acting on the control currents of the conveyors, is equal to 11.3 MHz for I/sub 0/=20 /spl mu/A and to 16.6 MHz for I/sub 0/=30 /spl mu/A. This variation produces very small changes in both the quality factor and the gain (variations less than 7%). Comparisons between existing OTA circuits and the ones implemented from controlled conveyors, are also given. They underline the advantage which result from implementations using controlled conveyors.

High frequency applications based on a new current controlled conveyor

A novel current-mode biquad using only operational amplifiers (OAs) and multiple current output operational transconductance amplifiers (OTAs) is introduced. The proposed circuit can realise five different biquad transfer functions simultaneously. This circuit enables the circuit characteristics to be electronically tuned. An example is given, together with simulated results by PSPICE.

Current-mode biquad without external passive elements

Some novel multifunction biquadratic filters, each of which employs two to three operational transconductance amplifiers and two capacitors, are presented. Each proposed circuit offers the following advantageous features: realization of different biquadratic filter signals from the same configuration, no requirements for component-matching conditions, employment of only two capacitors, control of /spl omega//sub o/ and /spl omega//sub o//Q, with separate tunable transconductances and low sensitivities.

New multifunction OTA-C biquads

A novel mixed-mode biquad circuit is presented. The circuit uses six single-output- and one dual-output-operational transconductance amplifiers, two grounded capacitors; and can realize lowpass, highpass, bandpass, notch, lowpass-notch, highpass-notch and allpass responses from the same topology. The circuit can be driven by voltage or current and its output can be voltage or current. The parameters ωo and ωo/Q o enjoy independent electronic tunability. Simulation results are included.

A novel mixed-mode OTA-C universal filter

A universal current mode operational transconductance amplifier-capacitor (OTA-C) biquad with three inputs and four outputs employing the minimum of components: only two OTAs and only two grounded capacitors is presented. The proposed circuit offers the following advantageous features: realization of low-pass, bandpass, high-pass, notch; and all-pass signals from the same simple configuration, employment of two grounded capacitors ideal for integration and low-sensitivity performance.

Universal current-mode OTA-C biquad with the minimum components

A new way to implement current-mode continuous-time filters is presented which uses operational transconductance amplifiers (OTAs). Based on the simulation of a signal flow graph on the all-pole lowpass transfer function, the two current-mode realizations of high-order OTA-C filters are obtained.

Current-mode high-order OTA-C filters

A new active-C biquadratic filter structure is presented which uses four OTAs and two capacitors. The circuit can simultaneously provide three filter outputs in a single structure and it realizes all standard second-order filters from each output of the circuit.

New multifunction active filter using OTAs

A new switched-capacitor (SC) universal biquadratic fitter is presented. The circuit uses three operational amplifiers and can simultaneously realize lowpass, bandpass and highpass transfer functions in a single SC structure. The filter is parasitic free, requires less capacitor spread and total capacitance, and enjoys very low sensitivities.

Jie Wu

Papers

Current-mode high-order OTA-C filters

New multifunction active filter using OTAs

New switched-capacitor universal biquadratic filter