by michael1978
Tags: amplifier, transistor
P: 133
 Quote by Jony130 I don't know why. Maybe you made a mistake in simulation program.

yes Jony, i do it one more time and is now 0,68 Vac now smaller, of i have to change the emitter capacitor , because the value of capacitor i make 1000u, of transistor , wich transistor you think to use do you know some type?
because input is 2mv*50gain=100MV
 HW Helper Thanks P: 5,465 The BC109C is a popular high gain general purpose transistor.
P: 133
 Quote by NascentOxygen The BC109C is a popular high gain general purpose transistor.
i will change now

i dont have that type of transistor
 P: 133 look my circuit, i dont know where i make mistake, normal gain have to be 50*2Mv=100mV Peak Attached Thumbnails
 HW Helper Thanks P: 5,465 It's not a very good design. For bias point stability (against VB and ß variations) you should allow a couple of volts across the emitter resistor; you have just 0.4V. For maximum symmetrical output swing, you should allow approx as much voltage across RC as VCE. But you have ~1.8V and 7.8V, resp. At what frequency are you measuring the ac gain?
 P: 410 No the design is good. Simply the BJT that michael1978 use in his simulation has a very low current gain. Ie = 0.4V/220Ω = 1.8mA And Ib = IR4 - IR5 IR4 = 1V/30K = 33.4μA IR5 = (10V - 1V)/150kΩ = 9V/150KΩ = 60μA So Ib = 60μA - 33.4μA = 26.6μA And Hfe = β = (Ie/Ib - 1) = 66.6 And this circuit was design for Hfe > 420
P: 133
 Quote by NascentOxygen It's not a very good design. For bias point stability (against VB and ß variations) you should allow a couple of volts across the emitter resistor; you have just 0.4V. For maximum symmetrical output swing, you should allow approx as much voltage across RC as VCE. But you have ~1.8V and 7.8V, resp. At what frequency are you measuring the ac gain?
at 20kh
P: 133
 Quote by Jony130 No the design is good. Simply the BJT that michael1978 use in his simulation has a very low current gain. Ie = 0.4V/220Ω = 1.8mA And Ib = IR4 - IR5 IR4 = 1V/30K = 33.4μA IR5 = (10V - 1V)/150kΩ = 9V/150KΩ = 60μA So Ib = 60μA - 33.4μA = 26.6μA And Hfe = β = (Ie/Ib - 1) = 66.6 And this circuit was design for Hfe > 420
so result is correct 66.6, for ib like this is formula for current Ir5-Ir4? is not the same for ir4 and ir5 they are in serie ir4 and ir5
but Jony you told Ve to be 1v why is now Ve 0.4V?
P: 133
 Quote by michael1978 so result is correct 66.6, or voltage gain is 66.6, if so 66.6*2Mv=133mv again the result is not corrcect for ib like this is formula for current Ir5-Ir4? is not the same for ir4 and ir5 they are in serie ir4 and ir5 but Jony you told Ve to be 1v why is now Ve 0.4V? thnx for reply
]so result is correct 66.6, or voltage gain is 66.6, if so 66.6*2Mv=133mv again the result is not corrcect
for ib like this is formula for current Ir5-Ir4? is not the same for ir4 and ir5 they are in serie ir4 and ir5
but Jony you told Ve to be 1v why is now Ve 0.4V?
P: 133
 Quote by michael1978 thnx for reply ]so result is correct 66.6, or voltage gain is 66.6, if so 66.6*2Mv=133mv again the result is not corrcect for ib like this is formula for current Ir5-Ir4? is not the same for ir4 and ir5 they are in serie ir4 and ir5 but Jony you told Ve to be 1v why is now Ve 0.4V? thnx for reply

hi Jony, can you answer me please
P: 410
 Quote by michael1978 thnx for reply ]so result is correct 66.6, or voltage gain is 66.6, if so 66.6*2Mv=133mv again the result is not corrcect for ib like this is formula for current Ir5-Ir4? is not the same for ir4 and ir5 they are in serie ir4 and ir5 but Jony you told Ve to be 1v why is now Ve 0.4V? thnx for reply
66 is a BJT current gain, not a amplifier voltage gain.
So in order to make this circuit work properly. You need change the BJT that you use in your simulation program. You need to find the BJT with Hfe > 300 in your simulation.
P: 133
 Quote by Jony130 66 is a BJT current gain, not a amplifier voltage gain. So in order to make this circuit work properly. You need change the BJT that you use in your simulation program. You need to find the BJT with Hfe > 300 in your simulation.
ah 66 is curent gain, so you mean to change type of transistor, but is possible for you to tell me any type of transistor wich work, because there are a lot of type of transistor, and somebody he tell me one type of transistor but that transistor dont exist in my list of transistors
and yes Jony if you can tell me, i try to find self soms but i cant find it, that is the problem