Tài liệu Circuits & Electronics P8 pptx

6.002 CIRCUITS ANDELECTRONICS Dependent Sources and Amplifiers... Another dependent source example... Another dependent source example... An amplifier is a 3-ported device, actuallyWe of

6.002 CIRCUITS AND

ELECTRONICS

Dependent Sources

and Amplifiers

„ Nonlinear circuits — can use the

2-terminal 1-port devices

I i

I v

f I

Dependent Sources: Examples

V R

R I

V = 0

+–

V R

I i

I v

V R

Dependent Sources: Examples

K IR

=

oror

Example 2: Find V

( )

V

K V

f

+–

V R

e.g K = 10 -3 Amp·Volt

R = 1kΩ

Dependent Sources: Examples

Another dependent source example

Another dependent source example

Another dependent source example

Find v O as a function of v I

I

v +–

I v

Another dependent source example

0

=+

+

−V S i D R L v O

KVL

L D S

Next, Amplifiers

Try amplification

not bad!

noise

OL OH

V V

V

V

−

−

An amplifier is a 3-ported device, actually

We often don’t show the power port

Also, for convenience we commonly observe

“the common ground discipline.”

In other words, all ports often share a

common reference point called “ground.”

I v

0

=+

+

−V S i D R L v O

KVL

L D S

So, where’s the amplification?

Let’s look at the v O versus v I curve

K ,

V 10

~ 0.002.4

1.502.3

2.802.2

4.002.1

5.002.0

8.751.5

10.000.0

So is mathematically predicted behavior

One nit …

D i

If VCCS is a device that can source

power, then the mathematically

predicted behavior will be observed —

i.e

where v O goes -ve

I v O

v

If VCCS is a passive device,

then it cannot source power,

so v O cannot go -ve.

So, something must give!

Turns out, our model breaks down

Commonly

will no longer be valid when v O ≤ 0

e.g i D saturates (stops increasing)

and we observe:

I v

O

v

1