GB2078034A

GB2078034A - An audio phase splitting detector

Info

Publication number: GB2078034A
Application number: GB8038549A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-12
Filing date: 1980-12-02
Publication date: 1981-12-23

Abstract

The purpose of the Audio Phase Splitting Detector is to provide, by means of two opposite polarity connected diodes 2a, 2b, two audio signals one hundred and eighty degrees out of phase to drive a single ended class AB push-pull radio receiver output stage, as an alternative to using either a phase splitting driver transformer or a PNP plus NPN transistor combination. The output stage 8a - 8d may alternatively include two transistors (8a, 8b Figure 1). Two gauged potentiometers 4a, 4b control simultaneously the volume level of the output signals from the diodes <IMAGE>

Description

SPECIFICATION A phase splitting detector In the accompanying drawing 1/1 Figure 1, part 1 is the secondary winding of the final intermediate frequency transformer of a superheterodyne radio receiver, parts 2a and 2b are semiconductor detector diodes such as type OA 81 with their polarities connected as shown in Figure 1 to provide two audio signals of opposite phase, assuming of course the receiver is tuned to an ordinary amplitude modslated carrier with neither of the sidebands or carrier parts being suppressed.

Parts 3a and 3b in Figure 1 are 1 nF smoothing capacitors, parts 4a and 4b are a two gang potentiometer of approximately 5K Ohm resistance and is the volume control. Parts 5a and 5b are direct current blocking capacitors of approximately 8 mmF, 25 Volt D.C. working but allow the two audio signals derived from parts 2a and 2b, the detector diodes, to drive the output transistors parts 8a and 8b respectively.

OC 81 or their equivalents may be used for parts 8a and 8b in Figure 1 or if more amplification and output power is required four output transistors are used, parts 8a and 8c, 8b and 8b connected as shown in Figure 2 of the accompanying drawing 1/1. The resistors shown as parts 6a and 7a, 6b and 7b in Figure 1 provide base-bias current and resistors, parts 9a and 9b D.C. thermal stabilisation for the output transistors, parts 8a and 8b and are about 3 Ohms in value and finally parts 10 and 11 respectively are a D.C. blocking capacitor of about 50 mmF, (25 Volt D.C. working) and a loudspeaker of about 15 Ohm speech coil impedance.

The circuit in Figure 2 works identically as the circuit in Figure 1 but uses four transistors parts 8a and 8c, 8b and 8d to provide more output power than the arrangement in Figure 1.

The main advantages of this herein described arrangement are that no driver or output audio transformers are required, nor, as in othertransformerless designs, a mixture of NPN and PNP transistors are needed to phase-split the incomming audio signal: this being done by the two diodes, parts 2a and 2b, through being connected in opposite polarities respectively. The main disadvantage is the need for a two gang volume control potentiometer and in the Figure 1 version in the accompanying drawing 1/1, a much greater intermediate frequency signal than that needed to drive more conventionally designed circuits.

1. An electronic system whereby two diodes are connected in opposite polarity directions to the intermediate frequency or where appropiate radio frequency output stage producing by demodulation two balanced audio outputs one hundred and eighty degrees out of phase.

2. The use of a two gang potentiometer to control simultaneously the volume level of the output signals from the diodes.

New claims or amendments to claims filed on 24/6/81 Superseded claims 1 and 2 New or amended claims: WHAT I CLAIM IS:- 1. An amplitude modulated radio or intermediate frequency source, such as a coupling winding to a tuned circuit, (see Figures 1 & part 1 on the drawing sheet 1/1), of which the live side is connected in common to the anode of one demodulating diode and the cathode of a second but similar demodulating diode, and in series, with or without an R.F. filter, two gang volume control or both and with the base inputs of a single-ended push-pull amplifier.

2. The earthy end of the aforeinsaid amplitude modulated radio or intermediate frequency source is connected to the junction of the collector of one and the emittor of the other (or if there is direct current temperature stabilisation, the emittor series resistor of the other) see Figure 1 parts 9a & 8b or Figure 2 parts 9a & 8a respectively.

3. The single-ended push-pull amplifier herein substantially described uses either both NPN or both PNP transistors but not a mixture of the said types.

4. For higher audio output, four transistors may be used as shown in Figure 2 of the drawing sheet 1/1.

5. A radio receiver using the audio phase splitting detector output circuits as hereinbefore substantially described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A phase splitting detector In the accompanying drawing 1/1 Figure 1, part 1 is the secondary winding of the final intermediate frequency transformer of a superheterodyne radio receiver, parts 2a and 2b are semiconductor detector diodes such as type OA 81 with their polarities connected as shown in Figure 1 to provide two audio signals of opposite phase, assuming of course the receiver is tuned to an ordinary amplitude modslated carrier with neither of the sidebands or carrier parts being suppressed. Parts 3a and 3b in Figure 1 are 1 nF smoothing capacitors, parts 4a and 4b are a two gang potentiometer of approximately 5K Ohm resistance and is the volume control. Parts 5a and 5b are direct current blocking capacitors of approximately 8 mmF, 25 Volt D.C. working but allow the two audio signals derived from parts 2a and 2b, the detector diodes, to drive the output transistors parts 8a and 8b respectively. OC 81 or their equivalents may be used for parts 8a and 8b in Figure 1 or if more amplification and output power is required four output transistors are used, parts 8a and 8c, 8b and 8b connected as shown in Figure 2 of the accompanying drawing 1/1. The resistors shown as parts 6a and 7a, 6b and 7b in Figure 1 provide base-bias current and resistors, parts 9a and 9b D.C. thermal stabilisation for the output transistors, parts 8a and 8b and are about 3 Ohms in value and finally parts 10 and 11 respectively are a D.C. blocking capacitor of about 50 mmF, (25 Volt D.C. working) and a loudspeaker of about 15 Ohm speech coil impedance. The circuit in Figure 2 works identically as the circuit in Figure 1 but uses four transistors parts 8a and 8c, 8b and 8d to provide more output power than the arrangement in Figure 1. The main advantages of this herein described arrangement are that no driver or output audio transformers are required, nor, as in othertransformerless designs, a mixture of NPN and PNP transistors are needed to phase-split the incomming audio signal: this being done by the two diodes, parts 2a and 2b, through being connected in opposite polarities respectively. The main disadvantage is the need for a two gang volume control potentiometer and in the Figure 1 version in the accompanying drawing 1/1, a much greater intermediate frequency signal than that needed to drive more conventionally designed circuits. CLAIMS