In Figure 1, the 5V linear regulator (U1) delivers as much as 150mA of load current when operating by itself. Operating with the external pass transistor shown (Q1), the circuit maintains 5V ...

There appears to be 16 large transisitors which were mounted to the heatsink of this amplifier. It is a Planet Audio 4 channel car audio amp. From some quick Google searching, it looks like I should ...