Could someone explain to me hoe the pnp transistor in the attached ltspice circuit van amplifier the negative side of the current here.
The first npn has given only a postive current, there is no negative current involved here, I'm puzzled!

 

When the voltage on Q3 collector drops below the Q2 emitter voltage by ~0.6V, Q2 conducts.

 

Both Q1 and Q2 are acting as emitter followers.

The output voltage across R1 can go below ground *only* on the load (right) side of output coupling capacitor C2. The voltage on the left side of C2 never goes below ground. C2 charges up to DC voltage difference between the average value of the audio signal plus DC bias on the left, and GND on the right. In your circuit there should be approx. 7.5 Vdc across C2.

BUT - there is no negative feedback to stabilize the circuit operating point. With no input signal (V1 = 0 V), the voltage at the R3-R5 C2 node depends on the bias voltage at the Q3 base. The R3-R5 C2 node voltage will drift with changes in ambient temperature and component aging.

ak

 

Why is the load a 100 ohm resistor instead of an 8 ohm speaker?
The low current and low power output transistors are never used in an audio power amplifier. Use medium power transistors like3 TIP31 and TIP32 instead.
I agree that all audio power amplifiers have negative feedback that is missing here.

 

Could someone explain to me hoe the pnp transistor in the attached ltspice circuit van amplifier the negative side of the current here.
The first npn has given only a postive current, there is no negative current involved here, I'm puzzled!

Could you post a schematic in a graphic format?
I run LTSpice only in a dedicated PC.

 

Could you post a schematic in a graphic format?
I run LTSpice only in a dedicated PC.

@atferrari
Here's a copy of the TS schematic:

 

@atferrari
Here's a copy of the TS schematic:
View attachment 187027

Thanks