- Two transistors (usually NPN and PNP types).
- Resistors and capacitors for biasing and filtering.
- Transformer (for isolation and voltage transformation).
- Diodes for rectification (if needed).
- Transistors: The heart of the circuit consists of two transistors – one NPN and one PNP transistor. Commonly used transistors are NPN: 2N3904 and PNP: 2N3906.
- Base Biasing: Both transistors are connected in a push-pull configuration. The base of the NPN transistor is driven by one part of the input DC voltage, and the base of the PNP transistor is driven by the complementary part of the input DC voltage. This means that when one transistor is on (conducting), the other is off.
- Transformer: A center-tapped transformer is typically used to achieve the voltage transformation and isolation. The primary winding of the transformer is connected to the collector of the NPN transistor and the collector of the PNP transistor. The center tap of the primary winding is connected to the positive DC supply.
- Output: The secondary winding of the transformer is where the AC output is obtained. As one transistor conducts, it generates a positive half-cycle in the secondary winding, and when the other transistor conducts, it generates a negative half-cycle. The result is an alternating voltage at the secondary winding, which can be used as an AC output.
- Diodes (Optional): In some cases, diodes may be used across the transistors to handle back-EMF (electromotive force) or switching transients.
- Filtering: If a pure sine wave AC output is required, additional filtering components such as capacitors and inductors may be added to smooth the waveform.
In operation, the push-pull inverter alternates the conduction of the NPN and PNP transistors, resulting in a square wave or a quasi-square wave AC output at the secondary winding of the transformer. This output can then be further processed or filtered to obtain a sinusoidal waveform or used directly in applications where a square wave is acceptable.
Note that this is a simplified explanation, and practical push-pull inverters may include additional components and control circuitry to ensure proper operation and protection of the transistors and the transformer. The specific design parameters would depend on the desired output voltage, frequency, and power handling capabilities of the circuit.
When a DC voltage is applied to the provided circuit, T1 transistor begins conducting, allowing current to pass through N2 and R1 resistance. However, it’s important to note that the current passing through N1 does not immediately reach its maximum value; it takes approximately 5 time units to do so.
As the current through N2 gradually increases to its maximum, T1 is fully triggered, resulting in a high current passing through the N1 coil. The changing magnetic field generated by this current in N1 induces a voltage in the N3 coil. Additionally, it weakens the magnetic field in the N2 coil, causing the current passing through N2 to surge to a higher level. Once the currents passing through N1 and N2 reach their saturation points, the magnetic field around N1 stabilizes.
This stabilization causes the voltage in the secondary coil to drop to zero. Simultaneously, the pressure exerted by N1 on the N2 coil dissipates, leading to a decrease in the current through N2. As the current in N2 decreases, a magnetic field in the opposite direction to the previous one is generated, acting on N1.
This opposing magnetic force on N1, which in turn influences N2, drives the current in N2 down to zero. Consequently, the current through N1 also drops to zero, effectively resetting the circuit. Subsequently, a small current passing through N1 triggers the T2 transistor, and the circuit resumes its operation as described previously.
In essence, a transistor is a semiconductor device capable of both conducting and insulating electric current or voltage. It functions as a switch and an amplifier, enabling precise control and regulation of electronic signals in a compact form factor.