Abstract: A current amplifier circuit includes a first, second, third and fourth transistor, each having the same polarity. The first transistor is connected in series with the second transistor and both have the collector and base thereof electrically connected. The third and fourth transistors are connected in series and the fourth transistor has a resistor connected between the base and collector. The third transistor has its base connected to the collector of the first transistor. A bias current is applied to the collector of the first transistor and an input current to be amplified is applied to the base of the fourth transistor. An amplified output current is obtained across the collector to emitter of the third transistor. In a differential amplifier circuit, a fifth transistor having the same polarity is connected with its base connected to the collector of the fourth transistor through a resistor.

Abstract: A comparator which sets the comparison level depending on the number of transistors used easily ascertains the relative accuracy of the load resistors, is suitable for integration and improves the relative accuracy of input DC biases.

Abstract: A current amplifier circuit has a first transistor with a collector and a base which are electrically connected, a second transistor connected in series with the first transistor and having a collector and a base which are electrically connected. A third and fourth transistor are connected in series with the collector of the first transistor connected to a base of the third transistor and the collector of the second transistor connected to a base of the fourth transistor through a resistor having a resistance R. The first, second, third and fourth transistors have the same polarity. An amplified output signal current R.multidot.i/R.sub.E is obtained from a collector of the third transistor, wherein R.sub.E is the emitter resistance of the fourth transistor and i is the input signal applied to the base of the fourth transistor.

Abstract: A current mirror circuit of the present invention has the structure that the diode-connected second transistor is connected in series to the first transistor, the third and fourth transistors have bases which are respectively connected to the bases of the first and second transistors which are connected in series, and the collector of the fifth transitors, whose emitter and base are connected between the base and collector of the first transistor, is connected to the collector of the fourth transistor.