Patent GB-1425527-A (GB)
Title: Circuit arrangement including an integrated current injecotr
IPC: H03G3/34
Filed: 1973-03-22
Abstract: 1425527 Integrated circuits; deaf aid circuits PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 22 March 1973 [25 March 1972] 13857/73 Headings H3T and H4J In a circuit arrangement comprising a circuit element A1, A2, Fig. 1, T110, Fig. 9, a current injector I110 integrated with the circuit element for supplying the circuit element T110 with current, and current control means S having an output connected to a bias current input of the current injector, the circuit element A1, A2, T110 is included in a signal channel a point on which is coupled to a control input of the current control means S for adjusting the output current of the current control means S to a first value in response to a first category of signal at an input of the channel, and to a second value such as a standby value in response to a second category of signal at an input of the channel. A current injector is a multilayer structure having an injecting layer (1, Fig. 6, not shown) an intermediate layer (3) and a collecting layer (2) which layers are separated from each other by rectifying junctions and in which the collecting layer (2) forms with an adjacent layer of the current injector, a zone of the circuit element to be supplied with current belonging to the collecting layer. A structure of this kind is described in Specifications 1,398,862/3/4/5/6/ 7/8. The current injector can be a lateral structure having a P type layer (1) connected to a supply source, a N type intermediate layer (3) connected to earth and a P type layer (2). Layers (4, 5) constitute the two collectors of a multi collector transistor formed by the layers (3-2-4/5). The current injector layers (1-3-2) can be constructed as a vertical structure and the transistor layers (3-2-4/5) as a lateral structure. The Specification discloses how current injectors may be provided in known manner in an integrated circuit comprising complementary transistors (T91, T90, Figs. 7 and 8, not shown). A vertical transistor (T90) operates in the linear range and has emitter, base and collector regions (105, 106, 107 and 108). The collector (108) is formed by a layer containing metal, such as Al, provided on the base zone (107) and which forms a Schottky junction with the base zone (107). A lateral transistor (T91) has emitter, base and collector regions (107, 105, 106 and 110) and a current injector is formed by zone (107), intermediate layer (105 and 106) and zone (110) and constitutes two current sources (I90, I91). In a block diagram of the circuit arrangement Fig. 1, an input signal at K1 is amplified in a preamplifier A2 and when the control S detects the first signal the amplifier A1 is controlled with a large supply current so as to provide an amplified output in loud-speaker E. If the second signal is detected the supply current for the amplifier A1 is adjusted to the standby value. The terminal K1 may be connected to an antenna and the signal then consists of a carrier. The amplifier A1 can be followed by a logic processing unit which recognizes the specific signal frequency and actuates the signalling unit E. This device can operate as a portable telephone the specific signal frequencies constituting the calling code. When there are no calls the amplifier A1 is in the standby state. A modified portable telephone having a decoder (DEC, Fig. 10, not shown) between the amplifier A1 and the signalling unit E is disclosed. The terminal K1 may be connected to receive an acoustic signal as in a linear amplifier for a hearing aid shown in Fig. 9 where the output from K2, K3 is used to control a switch in the power supply lead to current injectors I110-I112 to switch from a standby current to a larger current when a signal is received. In a modification of Fig. 1, the power to the preamplifier (A3, Fig. 2, not shown) is also controlled from the control S between the standby and higher current values. In a further modification (Fig. 5, not shown) the amplifiers A1, (A3) are replaced by a single amplifier (A13) the output of which is used to control the control S. The input terminal K1 may be connected to a signalling channel amplifier (A4, Fig. 3, not shown) which controls the control S and to a preamplifier (A5) of the main channel amplifier A1. The amplifiers can be replaced by filters or demodulators. The control S can be a single resistor bridged by a transistor which is controlled so as to enable short circuiting of the resistor.