# Can I make a sine wave inverter this way??

#### rockgro

Joined Sep 7, 2021
13
I recently saw this video where he uses SPWM to create a sine wave inverter.

But I have a different approach to this.
Can we create sine wave signals using a Wien-bridge oscillator circuit and then an Emitter follower circuit using a power transistor to deliver high current? Is that not correct??

#### tepalia02

Joined May 13, 2022
37
If you see the comment section, you'll see some criticism on the design and parts list. I think you'd better take those into consideration.

#### rockgro

Joined Sep 7, 2021
13
If you see the comment section, you'll see some criticism on the design and parts list. I think you'd better take those into consideration.
But I am asking about my idea! not what he did in this video!

My Idea:
Can we create sine wave signals using a Wien-bridge oscillator circuit and then an Emitter follower circuit using a power transistor to deliver high current? Is that not correct??

#### crutschow

Joined Mar 14, 2008
29,810
Can we create sine wave signals using a Wien-bridge oscillator circuit and then an Emitter follower circuit using a power transistor to deliver high current? Is that not correct??
In concept, yes, but not good way in practice.
Depending upon how much AC power you want, it has very low efficiency, and will waste a lot of power as heat.
That's why SPWM is used, as it has much higher efficiency.

#### Papabravo

Joined Feb 24, 2006
18,431
But I am asking about my idea! not what he did in this video!

My Idea:
Can we create sine wave signals using a Wien-bridge oscillator circuit and then an Emitter follower circuit using a power transistor to deliver high current? Is that not correct??
It will be much easier to do this investigation with a simulator. It is easy to do efficiency calculations and you can change your assumptions and compare the efficacy of various strategies.

#### rockgro

Joined Sep 7, 2021
13
It will be much easier to do this investigation with a simulator. It is easy to do efficiency calculations and you can change your assumptions and compare the efficacy of various strategies.
Ohh ok! Ig I need to try out and figure out the efficiency of this system!
But can u tell an estimated efficiency of this type of system?

#### Papabravo

Joined Feb 24, 2006
18,431
Ohh ok! Ig I need to try out and figure out the efficiency of this system!
But can u tell an estimated efficiency of this type of system?
Less than 50% for a conventional emitter follower with a BJT power transistor. You might see some improvement with a low Rds(on) MOSFET in a source follower configuration, but it will pale in comparison to an SPWM system. Hitting 90% is fairly typical. Getting to 95% takes some careful analysis, understanding and component selection. The next few %-age points will not come without considerable effort and skill.

#### rockgro

Joined Sep 7, 2021
13
Less than 50% for a conventional emitter follower with a BJT power transistor. You might see some improvement with a low Rds(on) MOSFET in a source follower configuration, but it will pale in comparison to an SPWM system. Hitting 90% is fairly typical. Getting to 95% takes some careful analysis, understanding and component selection. The next few %-age points will not come without considerable effort and skill.
Ok Thanks!!

#### nsaspook

Joined Aug 27, 2009
9,740
But I am asking about my idea! not what he did in this video!

My Idea:
Can we create sine wave signals using a Wien-bridge oscillator circuit and then an Emitter follower circuit using a power transistor to deliver high current? Is that not correct??
That's just not a practical way to convert power today. We once actually used large DC power bank supplied audio amplifiers as inverters for sensitive circuits before modern digital methods were practical.

With modern digital signal generation it's easily possible to have a few hundred watts of polyphase output power in a small package.