1.4 S-Series for Power Amplifiers A power MOSFET is excellent as an output stage because its high input impedance neatly separates theoutputcurrent amplification stage from the input voltage gain stage. This simplifies the input voltage gain stage, so low cost components may be used and no pre- driver stage is necessary. Bipolar Transistors may at first seem more suited to power amplifiers than MOSFETs as their transconductance is nearly forty times larger. However, negative feedback can be used to make any difference negligible. In addition, higher power Table 3 : S-Series Typical Characteristics Package Number P-Ch 2SK619 2SK1197 2SK1058 2SK317 2SK318 2SK410 output stages can easily be designed just by connecting extra power MOSFETs in parallel. This flexibility arises from the positive temperature coefficient of the power MOSFET, which gives the transistor the ability to share current. The combination of these features has made the S-Series MOSFETs very popular with the manufacturers of high power amplifiers. Some design engineers have claimed that this series gives their amplifiers an excellent Sound Quality not achievable with other MOSFETs. Unfortunately, this is one parameter Hitachi has found difficult to characterise. 0.15/0.1 180/230 60/110 250/230 90/120 9) 25 Notes : * = Vpsx ** ; Value at Tc = 25C *** : Test conditions : Vpg > Ip Rpsion)> Ip = 1) Ip max (DC) (H) : Specially manufactured for comm ur Peaticns te industry