A very simple inverter circuit using 4 transistor only is discussed in the following article, which can be quickly built by any novice in the field.
Referring to the circuit design below we can see that the inverter circuit uses just 4 transistors, a transformer, and a battery to implement a ful 100 watt power output from a small 12V 10 AH battery.
The circuit works with a push pull kind of operation where the Q1 and Q2 form a basic astable multivibartor for creating the basic 50 Hz frequency.
Q1 and Q2 could be any general purpose PNP transistor such as TIP127 or even a 2N2907 could be tyried for the purpose.
The two transistor conduct alternately, and therefore produce positive signals across there collectors which is fed to the subsequent power transistors consisting of the 2N3055 devices.
The Q1, and Q2 are able to produce strong alternating biasing current for the 2N3055 transistors which respond to these alternating conduction and begin oscillating with the same frequency, which in turn casuses high current from the battery to push and pull across the relevant transformer winding.
This alternating high current induction in the transformer primary generates an equivalent 220 or 120V AC across the secondary side of the transformer winding.
R3, and R4 could be reduced even further for generating higher power from the proposed simple inverter circuit using 4 transistors