Specialized Push–Pull Current Amplifiers for Analogue Signal Converters

Abstract

There has been analyzed the construction of specialized push-pull direct current amplifiers with increased linearity of the transfer characteristic based on the method of balancing cascade currents, which are used to build converters of analog signals. The schemes of specialized push-pull direct current amplifiers with bidirectional paraphase outputs proposed by the authors are considered. The specificity of the current balancing method based on the bi-directional current reflector and the bi-directional phase-splitter of the input current, is analyzed. Analytic expressions are obtained for the components of the output currents of the input push-pull cascade. The circuits of the balancing and amplifying cascades with two and four outputs, which are used in the intermediate stages of push-pull direct current amplifiers, are also given and analyzed. Analytic expressions are derived for the calculation of low-signal current gain factors, both for individual components of the output currents and the through transmission factor in the balance mode. In addition, an expression is obtained for the through small-signal gain factor, and also the dependences showing a change in the overall through transmission factor within the range of the output signal are also given. Linearity errors resulting from these changes are analyzed. A practical scheme of a high-linear current-to-current converter based on a push-pull phase-splitter of the input current and a block of balancing of amplified currents with two pairs of bi-directional outputs is considered. Schematic modeling of this current-to-current converter has been carried out using integrated transistor models. Recommendations are given for constructing on the basis of these push-pull direct current amplifiers current-to-current converters and voltage-to-current with low linearity errors, which makes it possible to use them in multichannel analog-to-digital converters.