摘要:

The operation of transistors in the avalanche mode provides simple but effective means for generating fast pulses. With present transistors there is a large spread of avalanche voltage between individual specimens, and the paper describes a method of designing trigger circuits which require no adjustment when transistors are changed.Some selection of transistors is necessary for fast operation, and it was found that of the transistors tested, which had α cut-off frequencies in the region of 10 Mc/s, about 20% had avalanche rise times less than 10 millimicrosec, 10% less than 3 millimicrosec, and 5% less than 1.5 millimicrosec. Circuits are described for generating pulses with rise times of 1 millimicrosec and having any width from 1 millimicrosec to several microseconds at half height.The collector current of an avalanching transistor may build up to 0.5 amp in a few millimicroseconds and no suitable diodes have been found for shaping such waveforms. However, good results have been obtained by using the non-linear capacitance of diodes biased in the reverse direction.Particular attention is paid to threshold stability and the generation of pulses accurately delayed in relation to the trigger pulse.An example of a practical application of these circuits is a wide-band oscillograph described in Reference 8.

DOI:10.1049/pi-b-2.1959.0149

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The advent of high-frequency transistors has created a need for improved oscillographs. Present instruments are neither fast enough nor sufficiently sensitive to display the low-amplitude high-impedance waveforms generated by these high-frequency transistors. A transistor oscillograph using the sampling principle has therefore been designed having a response extending from d.c. to 300 Mc/s, corresponding to a rise time of about 1.5 millimicrosec, and a sensitivity which gives a full-scale deflection for an input of a few hundred millivolts; the input impedance is equal to 1 pF and 1 megohm parallel. With one exception, all the transistors employed have α cut-off frequencies in the region of 10 Mc/s.A basic oscillograph using a total of ten transistors is described the first part of the paper, followed by a more sophisticated version with improved linearity and double-beam display.

DOI:10.1049/pi-b-2.1959.0150

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Any large-scale digital equipment, such as a computer, requires a number of timing waveforms. In general, these are produced by central pulse-generating equipment and are then distributed throughout the system. In the design of transistorized systems, certain problems arise, principally owing to the limited power output of transistors and their relatively slower switching speeds compared with hard valves. As a result, considerable difficulty is experienced in ensuring adequate synchronism between the different waveforms. An automatic method of maintaining synchronism by means of servo control system has therefore been developed. The output waveforms are examined and compared, and correction signals are generated which control variable-delay devices inserted in the appropriate amplifier chains.

DOI:10.1049/pi-b-2.1959.0151

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The circuits described use transistors as bidirectional switches in conjunction with bistable circuits and short delay lines. The bistable circuit is of a type from which registers used in a digital computer may be assembled. By connecting bidirectional switches in various ways between digits of registers, any one of the operations of transfer, exchange, shift and count can be carried out in a time less than 0.2 microsec. The transistors used in the bistable circuit and for bidirectional switches are of the surface-barrier type. The delay cable provides a delay of 60 millimicrosec.

DOI:10.1049/pi-b-2.1959.0152

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0153

出版商:IEE    

年代:1959

数据来源: IET