A transistor in which the emitter terminal is coupled to ground through a filter capacitor. The filter capacitor has a capacitance of from about 0.2 μf to about 22 μf and can be connected either by itself or in parallel with a resistor, depending upon the circuit in which it is used. The incorporation of a filter capacitor of such a capacitance level provides greatly improved gain and less distortion of the input signal, to permit a high output to be achieved in fewer amplifier stages and with less current draw and heating than in conventional transistor amplifier stage circuits. Additionally, the transistor can be provided in a unitary structure by incorporating the filter capacitor directly on the transistor chip, and can also be provided by incorporating the transistor and a resistor within the casing of a filter capacitor.

High gain, low distortion, faster switching transistor

A mobile audio system includes a mobile audio instrument having no internal amplifier, a first connector fixedly mounted on the back face of the instrument, a mounting and demounting unit for supporting the mobile audio instrument in a detachable manner, a second connector fixedly mounted on the mounting and demounting unit and having contacts each of which is electrically connected with the corresponding one of the contacts in the first connector and an external amplifier fixedly mounted on the mobile audio instrument and for amplifying line outputs from the second connector. Since the mobile audio instrument has no internal amplifier, the mobile audio system can be reduced in size and weight and improved for portability. In addition, the number of contacts can be reduced and the number of different types of contacts is decreased.

Mobile audio system

The PN junctions of a transistor are biased for operation in the active mode but an initial flow of current reverses the bias of the base-emitter junction causing the transistor to conduct a resonant current with a voltage less than the forward junction voltage of said base-emitter.

Resonant operating mode for a transistor

This chapter gives an overview on the way amplifier design has evolved in the past three or four decades. Designs using germanium devices appeared first, but suffered severely. Proper complementary power devices appeared in the late 1960s, and full complementary output stages soon proved to give less distortion than their quasi-complementary predecessors from the vulnerability of germanium to even moderately high temperatures. The vast majority of audio amplifiers use the conventional architecture, which is shown in the chapter. There are three stages of the architecture: a transconductance stage (differential voltage in, current out), a transimpedance stage (current in, voltage out), and a unity-voltage gain output stage. The chapter elaborates on these three stages of architecture. A two-stage amplifier is likely to be more complex in its gain structure than a three-stage amplifier. The chapter also discusses the power amplifier classes. All power amplifiers are either AC-coupled or DC-coupled. There is a huge body of knowledge devoted to the art of keeping feedback loops stable while optimizing their accuracy, which is called Control Theory. Technical bookshop yields some intimidatingly fat volumes like ‘Control System Design.’

Leslie E Scott

Papers

Transistor audio amplifier

Stabilized transistor oscillator circuit

Selective antenna tuning system for a transistor portable automobile radio receiver