Abstract: There is provided a gain control Gilbert amplifier circuit which can be more easily controlled for variation in the gain characteristics of each predriver integrated circuit for primary color image signals R, G, and B, and the variation caused by light emitting efficiency than the prior art. The gain control Gilbert amplifier circuit also operates in a wider frequency range than the conventional circuits, and has a large S/N ratio. One embodiment of the amplifier circuit comprises a grounded-base transistor amplifier circuit having rectifier elements, reference voltage sources, diodes connected to a differentially paired transistors. The rectifier elements are controlled so that a ratio of currents output from constant-current sources can be selected to enable the frequency characteristic of the amplifier circuit to expand by a frequency range.

Abstract: An automatic gain control circuit having a variable gain amplifier circuit, a signal level detecting circuit connected to the variable gain amplifier circuit for generating a detect signal the level of which changes in response to a signal level of an output signal of the variable gain amplifier circuit, and a gain control circuit for controlling the gain of the variable gain amplifier circuit in accordance with the signal level of the detect signal, and the gain control circuit having a differential amplifier circuit having first and second input terminals, the first and second input terminals being connected to the signal level detecting circuit for receiving the detect signal, a first reference voltage source connected to the first input terminal of the differential amplifier so that a first predetermined voltage is provided instead of the signal level of the detect signal in response to the signal level of the detect signal and a second reference voltage source connected to the second input terminal of th

Abstract: At the surface of an insulating substrate there are provided a working electrode and an counter electrode with a set space from the working electrode and a gas-permeable, proton-conductive film with which the surfaces of the electrodes are overlaid in such a manner as to form an integrated whole with the electrodes. By applying a set voltage between the two electrodes, flammable gas which has permeated the gas-permeable, proton conductive film is made to undergo oxidation and reduction at a surface of the working electrode, and protons which have been produced thereby move toward the counter electrode in the gas-permeable, proton-conductive film, so that the concentration of the flammable gas can be measured. A reference electrode can be provided for the purpose of stabilizing potential of the working electrode. A mechanism which is described above can be applied to a gas sensor of field-effect transistor type.