GB923655A - Improvements in or relating to electrical phase detectors - Google Patents

Abstract

923,655. Transistor circuits. GENERAL ELECTRIC CO. Ltd. Jan. 11, 1960 [Jan. 12, 1959], No. 11254/62. Divided out of 920,535. Class 40 (6). [Also in Group XXXVI] A phase detector circuit for determining the phase relationship between input signals at IL and RL includes a bi-stable circuit BC the state of which depends on the phase relationship between the input signals, the signal at IL varying the relative impedances of the two input paths (C2D2, C3D3) over which the signal at RL is applied to BC, so that the amplitudes of the pulses applied to the bases of T4T5 respectively will be different, the state of BC being dependent on which of these pulses has a larger amplitude. T2 will be conductive for negative cycles of the input at IL and T3 for positive cycles, and pulses of different polarity but of the same amplitude will appear at the collectors of T2, T3. When T2 is conductive, D2 will be more conductive than D3 and transistor T4 will either be cut-off or remain cut-off depending on its previous state, and when T3 is conductive D3 will be more conductive than D2 and T5 will be cut-off. Therefore, if the signals are in-phase, that is, the positive pulses derived from alternate cycles of the signal at RL correspond to the positive cycle of the input at IL, then T4 will conduct and T5 will be cut-off therefore giving a negative output at OL. In the antiphase condition T4 will be cut off and T5 conduct thus giving zero output at OL. The mean D.C. levels of the pulses appearing at the collector outputs is kept the same by the provision of a stabilizing circuit consisting of R7, R8 and C1.