| Title |
Accuracy Enhancement Technique in the Current-Attenuator Circuit |
| Keywords |
Current mode Circuit ; current-attenuator ; DC offset-current |
| Abstract |
To realize the tap coefficient of a finite impulse response(FIR) filter or the twiddle factor of a fast Fourier transform(FFT) using a current-mode analog circuit, a high accurate current-attenuator circuit is needed. This paper introduces an accuracy enhancement technique in the current-mode signal processing. First of all, the DC offset-current error in a conventional current-attenuator using a gate-ratioed current mirror circuit is analyzed and then, the current-attenuator circuit with a negligibly small DC offset-current error is introduced. The circuit consists of N-output current mirrors connected in parallel with one another. The output current of the circuit is attenuated to 1/N of the input current. On the basis of the Kirchhoff’ current law, the current scale ratio is determined simply by the number of the current mirrors in the N-current mirrors connected in parallel. In the proposed current-attenuator circuit, the scale accuracy is limited by the ac gain error of the current mirror. Considering that a current mirror has a negligibly small ac gain error, the attainable maximum scale accuracy is theoretically -80[dB] to the input current. |