HF correction due to frequency dependent OOS

t   _E = R _e S _e ;

C _o = C _out + C _w + C _n ;

R _e1 C _e1   - chain of automatic shift;

R _e S _e - chain of high-frequency correction ;

R1, R2 is a divisor;

R n - AC resistance;

R _e << R _e1 ;

C _e << C _e1 ;

R _e   "   (10-50) ohms

With _u   "   (10-500) pF

On HF, _RN - decreases ( w _S >> w _B ), therefore S does not depend on w , therefore Z _K decreases, gain decreases. This is due to the shunt effect C ₀ .

From the formula (*) of the gain with the OS, it can be seen that the depth F = 1 + SZ _E , will vary with frequency. Thus, with an increase in w, in the numerator, Z _K - decreases, and in the denominator F decreases (OS depth), thereby ensuring a constant gain in a certain frequency band. Choosing the appropriate elements of correction , you can get the rise of the frequency response and, therefore, reduce the settling time ( t _Y ).

We find the analytical expression of frequency response, phase response and PC with the corrected OOS.

R _OUT >> R _K ; R _OUT >> R _H.

At LF R _OUT >> R _K ; R _OUT >> R _H.

Using the accepted notation, we represent the characteristic in the form:

Using the Braude method, we find the optimality condition for frequency response, phase response, HRP.

The condition of optimal correction of the frequency response :

Equating the coefficients for the same degrees X _B = w t   _B , we get:

Consequently, the bandwidth expands to the depth of the OS.

These formulas work well if R _H >> R _K. When intermediate cascades work, efficiency decreases.

The sequence of calculation:

1) Determine F _e ;

2) Find m;

3) Find R _e , C _e (R _e ~ 0.1R _e1 ), where R _e1 is the emitter stabilization resistance.

PH:

correction with the help of OOS:

1) It is sufficiently effective if R _H > R _K , the effect of R _{H is} weakened due to parallel capacitive coupling;

2) corrections with the help of R _E C _E -chain allows to stabilize the gain

3) Allows the use of highly reliable elements (capacitors);

4) Provides multi-band cascades most effectively.