The present invention relates to an amplifier and a display using the former. More particularly, the present invention relates to an amplifier having a high cut-off frequency (i.e., capable of processing a wide-band signal) and a high amplification factor, and an extremely fine display using the amplifier.
It is difficult to produce an amplifier which has a high cut-off frequency and a high output. Considering an integrated amplifier, the high cut-off frequency implies that the respective transistors composing the amplifier have a high value of F.sub.T (i.e., the product of gain and bandwidth). For this product, the sizes of the respective transistors to be formed in a semiconductor substrate have to be made fine. Since these fine elements naturally have low breakdown voltages, a high output cannot be generated as in a power amplifier even if the operating supply voltage (V.sub.cc) of the IC is raised.
Conversely, if a high output is to be generated, the sizes of the respective transistors have to be enlarged, which increases the parasitic capacities of the respective transistors in a way which adversely affects the frequency characteristics.
Thus, the rise of the cut-off frequency and the improvement of the amplification factor of the amplifier are intrinsically contradictory to each other, thereby limiting their compatibility.
In developing a highly fine display, we have recognized that a demand is present for an amplifier which has a remarkably wide operating frequency band of 200 MHz and a remarkably wide output dynamic range of 0 to 200 V. It has been found impossible in the prior art because of the aforementioned reasons to provide a remarkably small integrated amplifier which has such a wide band and a high output.