• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 33 subscribers
  • Views 1011 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ULQ2004A hfe and Vi(off)

na na78
Guru 16770 points
Other Parts Discussed in Thread: ULQ2004A

Hi

We want to know hfe of ULQ2004A.

In our system, the input voltage 4.2V would be applied to ULQ2004A from MCU.

According to the block diagram (Figure 21 in the datasheet), Rb=10.5kohm.
So we are considering the following formula to calculate Ib.

Ib=(4.2V - Vb)/10.5k - Vb/(7.2k+3k)

Is our understainding correct?  If it is correct, we need the value of Vb.

1.
How should we estimate Vb?

2.
How can we have the hfe for the Ib obtained by above formula?

3.
Could you tell us the value of Vin(off)?

BestRegards

  • 0
    TI__Mastermind 24975 points

    Hello,

    I will get back to you soon on this post.

    Best,
    Michael

  • 0 in reply to Michael J Schultis
    TI__Mastermind 24975 points

    Hello,

    It is difficult to determine the exact value of Ib. What is more important is what you referred to as the hfe curve. Please find data below.

    1. It is not necessary to estimate Vb. I can tell you based on my measurements that with a Vin = 4.2V, the Iin will be close to 200uA.

    2. Please find the effective hfe curve attached below for the device. Note that this is the ratio of the output current to the total input current for the device.

    3. Vin(off) is when the Iin is 65uA typically. Based on the input impedance of the device, this would be expected to be around 1.35V. A measurement on the bench gave me about 1.43V. 

    Please note that all data provided is typical and is not a guarantee of the device as they were measurements on only a single device.

    Best,
    Michael