Hi guys,
I wanted to build a boost buck converter using 2N7000.
The converter is only working with low voltage, like 5V.
Is 2N7000 suitable for this application?

Please give me some suggestion

 

Welcome to AAC!
The 2N7000 can't handle much current. What output voltage and current are you hoping to get from the converter?

 

500mA for 2N7000 → https://www.fairchildsemi.com/datasheets/2N/2N7000.pdf
http://www.simonbramble.co.uk/dc_dc...nverter/sepic_buck_boost_converter_design.htm

http://www.ti.com/product/LM5118/datasheet/detailed_description

non of the parts alone makes your design
but setting limits to- / ranging- your design
may define the conversion frequency that sets requirements for inductors transistors mosfets diodes PCB design e.c.

from scratch it's always possible to make about 2kHz to 8kHz converter with the efficiency of about 60%
if you wan't to get a lot of output current/power your voltage regulation suffers , your efficiency may suffer at low voltage supplies . . .
(as a rule in web forums) not knowing your exact design parameters (web forum rule ends) it's difficult to tell

 

Welcome to AAC!
The 2N7000 can't handle much current. What output voltage and current are you hoping to get from the converter?

My application required only 0.2A to 0.5A and 3 to 8 voltage. I have checked the data sheet of 2N7000, the drain current is around 240mA. Therefore, I am not so sure whether 2n7000 can be used.

 

500ma in a pulsed application.
Max.

 

500mA for 2N7000 → https://www.fairchildsemi.com/datasheets/2N/2N7000.pdf
http://www.simonbramble.co.uk/dc_dc...nverter/sepic_buck_boost_converter_design.htm

http://www.ti.com/product/LM5118/datasheet/detailed_description

non of the parts alone makes your design
but setting limits to- / ranging- your design
may define the conversion frequency that sets requirements for inductors transistors mosfets diodes PCB design e.c.

from scratch it's always possible to make about 2kHz to 8kHz converter with the efficiency of about 60%
if you wan't to get a lot of output current/power your voltage regulation suffers , your efficiency may suffer at low voltage supplies . . .
(as a rule in web forums) not knowing your exact design parameters (web forum rule ends) it's difficult to tell

Sorry for left out the design parameter,
I have done some simulation about the converter. I have an input of 5V to drive a 12 V DC motor so that it can have different rpm. The current will be ranging from 0.2 to 0.5A.
The circuit is attached, from the simulation, the result seems to be desired. However, I am currently having only 2n7000 so not sure whether it can do the job. The load is modelled as a 14 ohms resistor.

 

No, it won't if you need 500 ma at 8v out, you would operating it beyond its current rating. To obtain reliable operation you need to either change your specification or change your transistor.

8 V x 500 ma = 4 Watts
4 Watts / 5 V = 800 ma

The above considers 100% efficiency and average current on the input but the peak current will be much higher.

 

the advantage of using ready made-s is that they're being tested and verified
the disadvantage is poor customizability
LT1930 -- are the industry's highest power SOT-23 switching regulators.
LT3580 -- a PWM DC/DC , can be configured as either a boost, SEPIC or inverting converter.

capable of generating 12V at 550mA or –12V at 350mA from a 5V​

http://cds.linear.com/docs/en/application-note/AN140fa.pdf