The 25W4GT is an indirectly heated, three-electrode, power receiving tube commonly used in the audio power stage of amplifiers. It was introduced by RCA in 1953 and is rated at 25 watts of power, with a 4 volt heater. It has a directly heated, oxide-coated nickel-iron grid, a graphite-coated, oxide-coated anode and an internally coated cathode. With its low-cost construction, the 25W4GT was a popular choice for audio designers, providing good performance and reliability. The 25W4GT has an internal voltage divider to maintain current balance between the anode and cathode when operating in pentode mode. The tube typically has a single-ended fixed bias arrangement, but is also capable of working in a variety of other topologies such as push-pull. The 25W4GT provides good power efficiency with its high transconductance, and is commonly found in guitar amplifiers and other audio applications.