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Phase Splitter With Wide Operational Margin

IP.com Disclosure Number: IPCOM000042488D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Keinert, J: AUTHOR [+4]

Abstract

A phase splitter is described which is largely independent of voltage tolerances and temperature changes. As the internal currents are kept constant over a wide range, the switching speed, too, has very small tolerances. The use of cross-coupled current mirrors as output stages, the constant internal currents and the relatively low switching levels make for low power consumption. Fig. 1 shows the circuit diagram. A current switch, comprising transistors T1 to T3, serves as an input stage. Its outputs A0 and A1 are connected to the bases of emitter followers T4 and T5, respectively. Emitter followers T4 and T5 and two interconnected transistor/resistor combinations T6, R6 and T7, R7 control the input levels D0, D1 of two current mirrors respectively comprising the transistors T8, T9 and T10, T11.

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Phase Splitter With Wide Operational Margin

A phase splitter is described which is largely independent of voltage tolerances and temperature changes. As the internal currents are kept constant over a wide range, the switching speed, too, has very small tolerances. The use of cross- coupled current mirrors as output stages, the constant internal currents and the relatively low switching levels make for low power consumption. Fig. 1 shows the circuit diagram. A current switch, comprising transistors T1 to T3, serves as an input stage. Its outputs A0 and A1 are connected to the bases of emitter followers T4 and T5, respectively. Emitter followers T4 and T5 and two interconnected transistor/resistor combinations T6, R6 and T7, R7 control the input levels D0, D1 of two current mirrors respectively comprising the transistors T8, T9 and T10, T11. In addition to level shifting, transistor/resistor combinations T6, R6 and T7, R7 compensate for tolerances of the supply voltage and temperature-dependent changes in the base-emitter voltages of transistors T4, T6, T11 and T5, T7 T9, respectively. Transistor/resistor combinations T6, R6 and T7, R7 are integral parts of a compensation network which also comprises a transistor/resistor chain T12, T13, T14, R12, R13 and a double current mirror made up of the transistors T15, T16 and T17. The base of T15 forms the input of the double current mirror. The magnitude of the currents in the double current mirror is determined by the transistor/resistor chain T12, T13, T14, R12, R13 linking the base of T15 with the supply voltage VCC. The outputs of the current mirror (collectors of T16 and T17) are connected to the bases of T6 and T7, respectively. As the three resistors R6, R7 and R12 have identical values and tolerances, identical voltage drops occur across the three resistors. Neglecting the voltage drop caused by the base currents, the following relation applies to the voltage drop VR at resistors R6, R7 and R12 of the compensation network: VR = VCC - 4 $ VBE. Decisive for the operation of the phase splitter is the voltage occurring at nodes B0 and B1 under the various permissible operating conditions. Since apart from the complementary mode, the behavior of the two output current mirrors is identical, the voltage at nodes B0 and B1 is calculated on the basis of the output current mirror comprising transistors T10 and T11. If input VIN of the phase splitter is a...